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ILLINOIS BIOLOGICAL 
MONOGRAPHS 


PUBLISHED QUARTERLY 
UNDER THE AUSPICES OF THE GRADUATE SCHOOL 
BY THE UNIVERSITY OF ILLINOIS 


VOLUME X 


Urbana, Illinois 


1926 


EDITORIAL COMMITTEE 


STEPHEN ALFRED FORBES WILLIAM TRELEASE 


HENRY BALDWIN WARD 


TABLE OF CONTENTS 


VOLUME X 


NUMBERS 

1. Studies on the Avian Species of the Cestode Family Hymenolepididae. 

7 By R. L. Mayhew. With 9 plates and 2 text figures.............. 
2. Some North American Fish Trematodes. By H. W. Manter. With 6 
plates; 2 charts jand Wtext: figures ts cece use ences ence geieeaee ess 

3. Comparative Studies on Furcocercous Cercariae. By H. M. Miller, Jr. 
With? plates and: 2 textifigures:c4 ca gwic te se ces tee oes ton he nae 

4. A Comparison of the Animal Communities of Coniferous and Deciduous 


Forests. By I. H. Blake. With 16 plates and 25 tables.......... 


PT OE IO 
d gti ¥ d Vas 


PAGES 


1-126 


127-264 


265-370 


371-520 


Digitized by the Internet Archive 
in 2011 with funding from 
University of Illinois Urbana-Champaign 


http://www. archive.org/details/comparisonofanim 10blak 


A COMPARISON OF THE 
ANIMAL COMMUNITIES OF CONIFEROUS 
AND DECIDUOUS FORESTS 


WITH 16 PLATES AND 25 TABLES 


BY 


IRVING HILL BLAKE 


ntributionst rom the 
Zoological La ee atory of the Univ is ae ae Illinois 
under the direc es no heres 


THESIS 


SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR 
THE DEGREE OF DOCTOR OF PHILOSOPHY IN ZOOLOGY IN THE 
GRADUATE SCHOOL OF THE UNIVERSITY OF ILLINOIS 


1925 


we 

v.1c 

TABLE OF CONTENTS 

Page 
An trod uctlom semiervese eieier ansratee cre tehnla) fescue el eucrsyes crass elsia chaypssus of 4/Fus:p @.dvecebaud 4.5 cocejenaso"y 7 
The Animal Ecology of the Upper Slopes of Mount Ktaadn.................-.-000 00s 10 
SCOMEIOLAW OL eet etree rasta eterna ta cue a ate esas Avstaveiasecs. soins a'eie: els  dler eco 10 
Phe*Ein vironment. ojy-svere = costs otra cte a falevaye ene, shal eleses)eiacedi'e aca sa vehe eis sip.ceyes wal sialtevesaral'e 11 
STEN igta cme er see eta reeetere orate clare cect erie tate Go staret sia etaie char roses Si drdaridrs Gicrstesrece 17 
Pardosa groenlandica (Rock) Associes.......... 2.000 c cece eee eee tenes 22 
Deltocephalus (Sedge) Associes............ cece cece cece eee nese neeeees 23 
Cymus discors (Sedge-Heath) AssocieS............ 0c cece eee eee eee e eee 25 
Pardosa uncata (Heath) Associes........... 00 0c cece cece ee eee eee e nena 26 
Linyphia nearctica (Krummholz) Associes.............0 ccc cece ee eee ees 27 
Rheumaptera hastata (Upper Forest) Association...............000 eee eee 29 
Sciurus hudsonicus (Spruce-Fir) Association. ............ 0.000 cece eee ees 30 
Aeschna’ (Pond-Bog):ASSOCleS 62. 5....e.a.cie 04 ve gu.g ties Sw coe ene ere meeieinsineioiace 32 
The Steep Slide Animal Community... 00. c cds ce caine ta nee eee oe eb ae 35 
Discussioniand SUMMALY <i e oa sicceherge ee ede See = ecieitis «swipe quessuesnale nee wewIne 36 
Wonclusions seer mine eer cst crt Mega, tere eerie ecto e ans even cates ee 38 
Animal Ecology of Maine Pine-Hemlock Forest... 2.0.2.0... ccc e cece eee eee 40 
SCOP ClOLMVV OMG cee eneneyaret numer sy rushed sf seayiepeieagen soya ours fansne Sestevaysie Shaye: skaielsiinsieeys: uclauevexce:e 40 
PETA VAL ODA CMG serge esse Soc ac) yeysns sai uc nescuarerstsyekan dates a ausnausrsiaians aareyavescherie ots eters 41 
PERE Biota ncitencteas ese os sie SNES OE Gigs wee ESSN EE obits dieiaienieisieisveiore 55 
Glastopteras(Shrutb) SOGleby sie. < corre fczyene.csa-e edn eave a dia erase Srayoreienaicye's steeds 59 
Heiobunum: (Herb) Society ss. acccecam ecco as cee > onicnmat cuca ara siueleeec 60 
Momocerusi(Meat):SOclety. «cas setae wi cteie sree cceterevoiweeraete!eenavatercanciels Scpavereal 62 
Aelodrilus (Sol) SOCIELY eye set eee esters erste ein dorsle lacie aleianchapere) sia Gansta eteners 62 
DISCUSSION ee bisteeis- scan cvavene chic sleds figteelos Selene AE SaieeG Cee Seale os wm auae tle suesove weleretnls 63 
Summary and Conclusion..............-.-..++0. Ee eR ee Se 66 
The Animal Ecology of Deciduous Forest in Winter ............0.00 0000 cee eee eee 67 
SCOPCOLWiOLK te crcts ca) ale sctel sues acs tiayel Ble es: ote! eeezepe ci sve Custentievone'e orminlee @aere's elecce 67 
UTWITORIMET Less cys coe sous wromine Seuereite Sauce aueinl ana eidlbs ocsealsysvaubia la: Sue's Misia ars'atecw aes 68 
PDTC Y 10 LA epg ote cacte er acynsi rete sisiare fiecz cis Se roan ote nevaustave cea uoa in Wain oa ee aieeisies 71 
Predominants of the Tomocerus (Leaf) Society............000 0c cece eens 76 
Predominants of the Fontaria (Top-Soil) Society... ...............00e ee eee 82 
Predominants of the Linyphia (Herb) Society (Autumnal).................. 83 
Vertebrates of the Winter Society’. i 2:.. ces nice bowie weeds Se seiele ee meee s 84 
Discussion: and SuMMArT Yes. 12.0 os ncusienaysuccrsae aa ntaaas sale mae ae ae eee 85 
Wonclusions tayo eee ee eae R oe sacs te Seaside eS SS Sanaa A eae doth aaa 88 
General Discussion and Summary. ....60:. 0.000050 eccb a dew ee nsieweetcneeneceweee. 90 
(OnGlUSIONS shee cas eae aaa see ens scis ee os h aoedcas a Alesis Sie. anene & elape) eee aes aura auelallelece alse wees 98 
MACKMOWIEGEEMENTS 2. tee cisc caves avevgd rd ccdndrh, sisal aga ada engrenies ME Mae Tee Re Qeci sews 99 
BUDO Fayence nance ct eee se ante cuacee od aul diceethis Aeorsystsldee imeiatrert ean Me easnaeees 100 
ETA ES epey epee ver tee EHS itt artes pti eee aie Meidyh ere nde ere dette alba Care lescte 104 


371] A COMPARISON OF ANIMAL COMMUNITIES—BLAKE 7 


INTRODUCTION 


The amount of detailed study given in the past to the community 
ecology (synecology) of land animals has been much less than that devoted 
to the ecology of particular species (autecology), a much older branch 
of the subject. One of the earlier studies in community ecology, from a 
modern aspect, was that of Davenport (1903), who studied the animal 
communities of a salt beach. The animal communities of deciduous 
forest, throughout developmental stages to the climax, have been described 
by Shelford (1912, 1913), with particular emphasis on succession, and its 
climax animal community by Adams (1915). Adams (1906, 1909) has given 
accounts of the animal ecology of northern coniferous forest, and he 
and his associates (1920) have published the results of an ecological 
reconnaissance into coniferous forest of the alpine type. These papers 
were qualitative rather than quantitative studies. 

Perhaps in part as a result of the valuable findings obtained in quanti- 
tative studies by various plant ecologists and by marine zodlogists, of 
whom Petersen (1911) may be cited as an example, more recent papers 
in synecology of terrestrial animals have shown a tendency towards 
the quantitative method of attack. This method has been employed 
by McAtee (1907), Beebe (1916), Wolcott (1918), Sanders and Shelford 
(1922), and Weese (1924). 

The present paper deals with the results of several studies of land 
animal communities and their habitats, made at different times under 
different environmental conditions. It is hoped to bring out some of the 
facts of the physical and biotic environments of the communities discussed, 
the composition of the communities as such, and their relation to certain 
ecological problems of succession, stratification and hibernation. The 
viewpoint, and with it the point of emphasis in investigation, has been 
different for différent portions of the work. In the study of the animal 
communities of the alpine coniferous forest and its predecessors, for 
example, the weight of attention fell on the process of succession of animal 
forms, and its relation to plant succession and response to physiographic 
and climatic conditions. When working in the coniferous forest of the 
low country, on the other hand, the interest of the investigation seemed 
to lie particularly in the problems of stratification, and the quantitative 
and qualitative distribution of the animal societies, as correlated with 
the results of instrumental measurements of such factors as temperature, 


8 ILLINOIS BIOLOGICAL MONOGRAPHS [372 


humidity, evaporation and light. The study of the deciduous forest commu- 
nity was essentially a winter study, and while carried on in the same way 
and with the same ends as the last, its emphasis fell naturally on hiberna- 
tion, and the responses of the animal societies of the lower strata to the 
climatic fluctuations. 

The following account of the results of these investigations may be 
subdivided into three parts: (a) a study of the animal ecology of alpine 
spruce-fir forest, including the various fell-field and tundra stages of which 
it is the climax, (Figs. 1, 2, and 3) (b) a summer study made in pine- 
hemlock forest at low elevation, with special emphasis on stratification, 
(Fig. 4) and (c) a winter study of the hibernating forest-floor population 
of elm-maple forest. (Fig. 5). 

The question of the ecological nomenclature employed calls for partic- 
ular discussion. It has been repeatedly insisted by various ecologists 
that biotic communities are in themselves units, and that at last analysis 
they should be so treated, both plants and animals being considered in 
their intrinsic and mutual relationships, as well as in relation to physio- 
graphic and climatic factors (Clements, 1920). A nomenclature covering 
plant communities in their various geographic, local, stratal and seasonal 
subdivisions has been long in use and often revised. A similar nomenclature 
for use in animal ecology was employed by Shelford (1925). The work of 
Weese (1924) employs an adaptation of the phyto-ecological nomenclature 
of Clements to the animal communities of deciduous forest. More recently 
the attempt has been made by Shelford and Towler (1925) to develop 
a nomenclature for biotic communities, based on both the plants and 
animals, and expressing in itself the taxonomic characteristics, permanence 
or the reverse, seasonal and stratal aspects, et cetera. In the present paper 
the writer has attempted to follow this classification of animal communities. 
It should be understood that the names of minor communities based on 
animals which were numerous in the author’s collections and appeared 
to be characteristic of the stratal and seasonal communities discussed, 
are put forward in the most tentative way. Several seasons of quanti- 
tative collecting should be done in the various strata of a single habitat, 
before the various sub-communities can be finally named after definite 
species, with any assurance that the species used are the characteristic 
predominants of the sub-communities named. 

in this discussion the term predominant will be used for species abun- 
dant in the habitat (and hence giving a part of its characteristic aspect) 
and for species affecting the habitat from any angle. The term is a general 
one. A dominant species is one whose effect on the general habitat is 
decisive, controlling its character and hence entire biota. 

True dominance appears to be a rare phenomenon among terrestrial 
animals, and is noted only in the few instances where, as in the case of 


373] A COMPARISON OF ANIMAL COMMUNITIES—BLAKE 9 


the short-grass plains of the western United States, herbaceous vegetation 
was probably kept in a sub-climax condition by great herds of grazing 
animals. 

In the case of denuded areas, the activities of tiger-beetles, digger 
wasps and spiders, feeding on insects blown in by wind, washed by waves 
or carried by the predominant predators, open the soil and add organic 
matter. A similar activity on the part of alpine invertebrates, especially 
spiders, was noted during this study. The animals in question inhabited 
the areas of rocks and bare soil produced by weathering and erosion. 
The animals do not control the habitat as do forest trees for example, 
but exercise an influence on both the habitat and the biota and are known 
as influents. 

Of the animals collected in sufficient numbers to be considered an im- 
portant part of the various communities, most exert a minor influence and 
are known as subinfluents. They may be defined as species which, because 
of restricted numbers, restricted stratal or seasonal occurrence or for other 
reasons, have a less effect on the habitat, or the biota balance of the 
community. Types of subinfluents noted were phytophagous insects, 
predaceous insects and spiders, and forest-litter animals such as spring- 
tails and millipedes, whose massed effects on changing the composition 
of decaying plant debris are of considerable importance to the habitat. 

Of less importance to the habitat as a whole is a species that is a domi- 
nule; such a species is said to be dominant ina microhabitat ofrestricted 
size, within the general habitat. Examples noted were groups cf phy- 
tophagous insects on their scattered host-plants, and groups of scavengers 
working on decaying organic matter, such as the body of a dead animal. 
Such dominules tend by their activities to destroy the microhabitat 
which they dominate (Shelford). 

Climax communities (Clements, 1916) which under existing climatic 
conditions will undergo no further change, have been referred to as associa- 
tions. Subclimax communities, in process of succession towards the climax, 
have been called associes. Seasonal communities, characteristic of different 
periods of the year, are spoken of as seasonal, and stratal communities, 
occupying different levels of the same habitat, as stratal socies or societies, 
depending on their permanence. 


10 ILLINOIS BIOLOGICAL MONOGRAPHS [374 


THE ANIMAL ECOLOGY OF THE UPPER SLOPES OF 
MOUNT KTAADN 


SCOPE OF WORK 


The work onwhich this study is based was done during a reconnaissance 
made in the summer of 1923. A base was established at an elevation of 
2,400 feet on Basin Pond, and another higher up at Chimney Pond, 
at an elevation of 2,900 feet. An outlying camp was maintained from time 
to time on the so-called Saddle, at an elevation of 4,275 feet. From these 
points the various stations were visited and studied, collecting being 
done at typical places. With the exception of a single maximum and 
minimum thermometer, instruments for the study of the environment 
were not available. In compiling the lists of animals for the various stations, 
certain species have been added from the literature and from information 
gained in correspondence, particularly in the case of vertebrates; the sources 
of this information have been given in all cases. Much more data could 
be gleaned from the published taxonomic lists, if the local habitats were 
given; as this is frequently not done, many species listed as occurring on 
Mt. Ktaadn are not included, since it was impossible to place them in 
the scheme of classification by habitats which was a part of the plan of 
study. Exceptions to this have been made in the cases of species. where 
the combination of elevation and restricted food habits of the animal 
make it possible, in the absence of other data, to assign it with some 
confidence to a given habitat. Where the habitat was known, or could be 
with reasonable certainty inferred, it seemed advisable, considering the 
general inaccessibility of the area and the small amount of zoological 
work that has been done there, to include what published records were 
available in the present lists. On the other hand, of the many species 
collected and determined, only such are considered here as approach, 
either numerically or otherwise, the status of predominants.* 

In considering the local environments of the various animal commu- 
nities, it has seemed wise to include rather full accounts of the plants 
found, taken in part from lists made in the field and in part from published 
work of various botanists. This is done in general to give as detailed 
an idea as possible of the animal habitats, and particularly to facilitate 
further studies of food relations of various phytophagous species to their 
environment. 


*Dominants of Clements (1920) and Weese (1924). 


375] A COMPARISON OF ANIMAL COMMUNITIES—BLAKE 11 


In general it may be said that the principal aim in this part of the 
investigation was to trace the process of animal succession from bare 
rock to forest, gaining what light was possible on its factors and causes. 


THE ENVIRONMENT 


The special ecological significance of Ktaadn is due primarily to its 
height. This is great enough—in a low and generally flat country—to have 
made its upper slopes a refuge for alpine species when, at the retreat 
of the last ice sheet, they were marooned by returning warm conditions 
(Adams, 1905). On the plant side it is quite obvious, even from a casual 
glance at the vegetation, that these arctic, or at least alpine species are 
being invaded by more mesophytic forms that are gradually spreading 
upward, in the face of severe handicaps of montane soil and climate. 
The persistance of their advance hints at eventual extinction of the less 
adaptable and less abundantly growing natives of the Arctic fell-fields. 
What is true of the plants will be seen to be equally true, even if less im- 
mediately obvious, of the animals of these upper regions of the mountain. 

The general topography of Mount Ktaadn and its relation to the sur- 
rounding country have been so often and so well described (Hamlin, 
1881; Tarr, 1900), that the writer will attempt no more than such a sketch 
as will render comprehensible the location and physiography of the areas 
studied. The location of the mountain is the north central part of Maine, 
between the eastern and western branches of the Penobscot river. It 
is stated by Harvey (1903a) to be 1°, 37’, 15”, or about 112 miles, north 
of Mount Washington, the highest point in New England, and is itself 
the second highest point. The general conformation is that of a long, 
table-topped mountain, rising rather abruptly from the surrounding 
country, and much less subdued, especially on the eastern face, than is 
the case with many other mountains of the northeastern United States. 
There are a number of special features other than height that should be 
considered from the standpoint of a biotic environment. 

First of these to be mentioned is area. Ktaadn is remarkable for the 
large extent of its upper regions, the entire mountain being about nine 
miles long and of varying width, the whole covering a very considerable 
area of alpine biota. The central plateau covers more than five hundred 
acres (Hamlin, 1881) and smaller areas of greater elevation on the south 
and larger areas in the vicinity of the northern peaks, increase to very 
respectable proportions the total alpine areas. Such opportunities for 
the study of mountain life over a considerable extent of territory are rare 
among eastern mountains, and for this reason Ktaadn presents to the 
ecologist some advantages over mountains that are its superiors in height. 
The equal exposure of the mountain to weather conditions on all sides, 
a fact caused by the isolation mentioned below, is another factor of some 


12 ILLINOIS BIOLOGICAL MONOGRAPHS [376 


importance in considering the habitat relations. Thus the effect of pre- 
vailing winds and other climatic factors on the mountain life show them- 
selves very plainly, uninfluenced by protection from neighboring heights. 
Another special feature, which will be seen to be important in the con- 
sideration of the environment of various communities, is that of drainage. 
The precipitation, as will be seen when the climatic factors are taken up in 
detail, is decidedly heavy as compared with that of coniferous forest at 
lower levels. But the rapid run-off on the steep slopes and the seepage of 
water from the scanty soil down among the underlying boulders on the 
level areas, combine with the high evaporating power of the air to rapidly 
remove the effects of the abundant rainfall. 

Certain features of the local topography are also of importance in 
determining the distribution of the various biotic associes. 

Portions of the walls of the glacial cirques, especially prominent on 
the eastern side of the mountain, are so steep as to support no life, being 
washed by water and scoured by the detritus of erosion of higher regions. 
If, however, there is any opportunity for soil and water retention, even 
here plant immigrants make good their stand, and at least a visiting 
animal population occurs. On the long dirt and rock slides conditions 
are more precarious, for frequent erosion gives plants little opportunity to 
establish themselves save at the borders of these slides, where conditions 
are somewhat more stable. Here is a characteristic biota, which seems 
to be in some respects a combination of types found in the various succes- 
sion stages on the plateau above. Plant succession on the plateau, which 
may be considered as typical of the process over most of the mountain, 
involves (Harvey, 1903a) successive associes of crustaceous lichens, 
reindeer-Iceland mosses, alpine tundra and krummholz, all leading up 
to the climax Picea-Abies forest of the entire region. This conception 
served as a general guide to the writer in selecting stations for study, 
although, as will be seen later, it seemed necessary in considering the 
animals to combine some of these stations and subdivide others. For 
the present we may accept the stages as given by Harvey and consider 
their local distribution. 

It is customary to consider the distribution of mountain biota as 
showing at least rough zonation with reference to altitude. This condition 
occurs on mountains sufficiently high to afford a true climatic timberline. 
Ktaadn, however, appears not to be high enough to possess such altitu- 
dinal zonation, and the local distribution of the various plants and animals 
is determined by other factors than those of altitude. For this reason we 
look in vain for any set altitudinal order of the various stages of succession, 
even under identical conditions of slope exposure. Just below the summit 
occur small mats of the climax trees, though dwarfed and prostrate from 
edaphic conditions and exposure to strong and continuous winds. On 


377] A COMPARISON OF ANIMAL COMMUNITIES—BLAKE 13 


the other hand, there are wide treeless areas at altitudes far below those 
of considerable growths of stunted but thickly-growing spruce and fir. 
In a similar way the earlier stages of plant succession, involving various 
steps from rock through alpine tundras to krummholz, appear wholly 
determined by physiographic and edaphic conditions, indubitably earlier 
stages occurring many hundreds of feet below older ones. This explanation 
is made in order that it may be understood why the various plant and 
animal associes are scattered in groups of various sizes very irregularly, 
and not necessarily correlated with altitude. Thus it will be seen that 
stations consisting of extensive areas of primitively bare rock may exist, 
as the one chosen for study did exist, considerably below the altitude 
where occurred a well established mat of alpine grasses and sedges, rep- 
resenting the second stage of tundra succession. 

The general topography of the mountain has already been discussed, 
particularly in its relations to biotic communities. Ktaadn is characterized 
among eastern mountains by its isolation, rising from the heavily wooded 
lower lands, with no serious rivals in its vicinity. Its gradual lower slopes 
rise, in most places to nearly three thousand feet, before terminating some- 
what abruptly at the steep ascent to the tableland and upper slopes. 
This upper region, which constitutes the mountain proper, has been de- 
scribed (Harvey, 1903-a) as a “long, narrow, fish-hook shaped, serrated 
crest, bristling with peaks and divided by the low central mountain, 
the ‘saddle’, into the North and South Mountains from which jut out 
spurs in all directions, enclosing several well-defined basins.” The highest, 
or West Peak, is in the southern group, with an elevation of 5,273 feet. 

The mountain is composed of granite, the lower portions being gray 
in color and hard, the upper red, and readily weathering to form at first 
a coarse, and later a finer, granitic soil. The character of the soil in the 
local areas studied will be taken up in more detail later. 

There have been no climatic studies made on Ktaadn, and little has 
been done in this regard on any of the New England mountains. The 
United States Weather Bureau maintained a station on Mount Washington 
(about 160 miles south and west of Mount Ktaadn) at an elevation of 
6,293 feet, duing the summer months of 1859, through the years 1871- 
1886 inclusive, and intermittently thereafter, mostly during the summer 
months, until 1892. Most of the data taken has been published, and some 
unpublished data have been kindly communicated by the Bureau. The 
University of Vermont maintained an observation station on Mount 
Mansfield (4,075 feet) during the summer of 1919, during which 
temperature, humidity, evaporation, wind velocity and sunshine were 
recorded. A short study was made on Mount Marcy (5,344) by Adams 
and his associates (1920), embracing temperatures, evaporation and solar 
radiation; this included only a period of five days. 


14 ILLINOIS BIOLOGICAL MONOGRAPHS [378 


The writer had at Ktaadn a maximum and minimum thermometer, 
whose reading had been corrected by a standard instrument. This was 
exposed in the shade of spruce-fir forest at Basin Pond (2,400 feet) from 
June 12 to July 29, with one break between July 23 and July 27. The 
station was that selected as the lower of two representing climax conditions 
(Station E). The results of these readings, a maximum and minimum 
for each twenty-four hour period, are shown as a graph (Fig. 8). It will be 
seen that the daily variations are considerable, and more marked, on the 
whole, for the maxima than for the minima. Even in the case of a shaded 
thermometer, the daily ranges are seen to be: 


Maximum Gis 
Minimum De 
Mean 9 
The temperature ranges between different strata, and between open 
and shaded areas, while not measured, must have been marked. 

From July 30 until August 18, with occasional interruptions due 
to absences on side trips, the same instrument was read twice daily in 
similar habitat at Chimney Pond, 500 feet higher (Station E-2). This 
point lies in the great South Basin, at the foot of the steep ascent to the 
highest peak, and has generally been considered as a region of climatic 
stress. It did not seem remarkable, therefore, that the daily ranges should 
be somewhat greater: 


Maximum 19.0°C 
Minimum eyelid ©: 
Mean 11.0°C 


Since these readings were taken during the latter part of the study, when 
the temperatures were gradually falling, as is indicated by the graph 
(Fig. 7), the comparison of the actual temperatures, as contrasted with 
the ranges, with those taken earlier at the lower station, cannot be of value. 
The entire data indicate a low summer mean temperature, varied by 
considerable extremes in both directions. 

On Mount Washington, the mean monthly temperatures as observed 
by the United States Weather Bureau for the years 1873 to 1886 in- 
clusive, are as follows, expressed in °C: 


January -17.8 July 8.9 
February -16.2 August 126 
March -14.5 September 3.4 
April° -6.8 October -1.8 
May -.3 November -9.7 
June 6.5 December -15.4 


379] A COMPARISON OF ANIMAL COMMUNITIES—BLAKE 15 


It will be seen from these figures that the temperature conditions expressed 
are relatively severe. The mean maximum temperature over the same 
period of years was 9.2°C the mean minimum temperature -20.8°C. 
The monthly mean minima are always below the freezing point. A portion 
of this data has been plotted as a hythergraph (Fig. 9), which will be 
discussed later. At present it may be pointed out that the mean monthly 
temperatures are distinctly lower, and the climate corresponding more 
severe, than that of Orono, lying considerably farther north, but with 
an elevation of only 129 feet. 

There are no instrumental studies of precipitation for Mount Ktaadn. 
The records from Mount Washington, however, are significant, and 
are in decided agreement with what has been observed and reported— 
but never actually measured—for Mount Ktaadn. Both mountains lie 
sufficiently near the sea to be, in general, subject to a maritime climate 
as distinguished from a continental one, modified by such factors as their 
altitude may serve to produce. The effect of this on precipitation is greatly 
augmented, as the upper slopes are sufficiently high to “intercept moisture- 
laden clouds and precipitation is almost daily and frequently excessive” 
(Harvey, 1903-a). On about half the days of the writer’s visit, there 
was more or less rain, either on the upper slopes or over the entire mountain. 
This was frequently of many days duration, and sometimes almost torren- 
tial in character. The mountain has always had a popular reputation for 
heavy precipitation. Judging from the recorded conditions on Mount 
Washington, as well as from the observations of various persons on Mount 
Ktaadn, the weight of precipitation must fall as rain during the warmer 
season. But the reports of lumbermen who worked from Basin Pond 
(2,400 feet elevation) for several winters, indicate the presence of a heavy 
winter snowfall. In general it may be said that abundant precipitation 
occurs, and the xerophytic aspects of some of the plant communities 
are due to other factors, such as rapid run-off and high evaporating power 
of air. The hythergraph (Fig. 9) gives the condition on Mount Washington. 
It will be seen that there is a large precipitation, well distributed, and 
falling more in the warmer portion of the year. 

The only study of evaporation on northeastern mountains, so far 
published is the short study of Adams (1920) on Mount Marcy, already 
referred to. Here there was a correlation between increased altitude and 
increased evaporating power of air, apparently modified for certain stations 
by the character of the plant cover and the amount of available moisture 
in the substratum. But even without measurements, it is evident that 
evaporation on the upper slopes is very great. The wind velocity, referred 
to below, coupled with the presence of only a thin soil and scanty plant 
cover, especially in the upper stations, makes for a high degree of water 
loss. In spite of the abundant rainfall, little or no standing water is found 


16 ILLINOIS BIOLOGICAL MONOGRAPHS [380 


in depressions of the rocks, except as these are of considerable size. The 
ground and alpine mat are soon dried on the surface after even the heaviest 
rain; the great evaporating power of the air thus offsets some of the effects 
of the large precipitation. 

The scanty data on air movement, aside from general observations not 
made with instruments, come from Mount Washington, where the average 
velocity over a period of twelve years was 105 miles per hour. The veloc- 
ities of wind on Mount Ktaadn are apparently of the same order, although 
there have been no measurements taken with instruments. It is a matter 
of common observation that very strong winds are the rule, and the vege- 
tation shows the same modifications of growth-form (Harvey, 1903-a) 
that have been described for the plants of the higher mountain. This high 
rate of wind velocity has been noted in connection with evaporation, 
and it no doubt increases the stress of the other climatic factors, such 
as temperature and precipitation extremes, in the effect on the biota. 

Studies on light are wanting, the nearest approach being the solar 
radiation studies carried on on Mount Marcy by Adams, with the aid of 
black and white spherical atmometers. These showed a general increase 
of light as the upper stations were approached, correlated with the de- 
creasing plant cover. 

In an attempt to get some idea of the conditions of the soils of the 
upper slopes, with particular reference to plant and animal succession 
through the various habitats, a number of soil samples were collected 
from various stations and later submitted to chemical and physical anal- 
yses. The results are given in Table I. Two important soil factors, tem- 
perature and hydrogen-ion concentration, were not investigated for lack 
of proper equipment. The results are of some interest, as showing certain 
apparent differences between tundra and early forest soils, in montane 
conditions. It will be seen that of the dry matter (the proportion of water 
not being considered as significant because of the time that elapsed before 
the analyses could be made) the greatest percent of inorganic material 
occurs in the sample taken from early (grass) alpine tundra at station C 
(Fig. 1), while the difference in this regard between the late (heath) 
alpine tundra at station C-2 and the early forest (krummholz) stage at 
Station D (Fig. 2) do not seem significant. Correlated with this is the fact 
that the first of the three soils named possesses the lowest organic content 
(39.6 parts per hundred) while the difference between the amounts of 
organic matter in the heath tundra and krummholz (respectively 75.5 
and 74.1 parts per hundred) is insignificant. It might appear from this 
that the qualitative changes from a purely mineral to a partially organic 
soil have taken place during the gradual transformation of grass to heath 
tundra, and that by the time the latter is reached the soil if deep enough 
is able to support the krummholz, as far as wind, moisture and other 
climatic conditions permit it to become established. 


381] A COMPARISON OF ANIMAL COMMUNITIES—BLAKE 17 


The nitrogen relations are less simple, and perhaps averages of further 
samples would alter them. They indicate a higher percentage of nitrogen 
for the late than for the early tundra, but a surprisingly low nitrogen per- 
cent for the krummbholz soil. Adams (1920) found a somewhat higher 
nitrogen value for the krummholz as compared with the tundra soil, 
as would naturally be expected. The acidity figure, given by titration 
with n/100 Ba(OH)s, is highest for the krummbholz soil; the relatively 
low acidity of the soil from heath tundra, as contrasted with that from 
grass tundra, is difficult to account for. It is likely that the investigation 
of the specific acidity of these soils by the methods of color indicators 
would yield more illuminating results. 

The primary soil formed by erosion of rock is at first a purely mineral 
one. With the process of biotic succession, the remains of organisms, 
beginning with the remains of the pioneer plants and animals, add more 
and more organic material. This is indicated by the increase of organic 
matter and corresponding decrease in purely mineral material, noted in 
the comparison of soils from early and late tundra stages. Itis an ecolog- 
ical truism that this process is accompanied by the process of plant succes- 
sion. The details of the accompanying animal succession, as observed 
in the alpine communities under consideration, will be considered. 


THE BIOTA 


The peaks and upper surfaces of Ktaadn display large rock areas, 
tundra-like stretches, and compact islands of krummholz. It is over these 
areas that the process of succession was studied. Before, however, going 
into the details of the various stations, and the plants and the animals 
found there, it will be necessary to say something of the animals of this 
upper region as a whole, and especially of the vertebrates, which from their 
larger size, better powers of locomotion, and superior powers of adaptation, 
show a more general distribution over the upper slopes, and less restriction 
to the minor succession stages than the invertebrates. In fact, with a very 
few exceptions which will be spoken of in due course, it might be said 
that the vertebrates of Ktaadn present two, and only two, great communi- 
ties, and that even between these two there is considerable overlapping 
of particular species, or rather, that one community, the climax, possesses 
a total vertebrate population inclusive of all or nearly all the species of 
the entire area, while the other, subclimax area is inhabited by a verte- 
brate population composed of certain species of the climax animals, 
while others do not appear in these early associes. It will be seen from 
a comparison of the tables (Tables II, III, IV, V and VI) that the number 
of vertebrate species appearing in the subclimax stages, but absent from 
the climax, is extremely small; indeed, perhaps a more extended investi- 
gation of the climax would show that there were none. These two commu- 


18 ILLINOIS BIOLOGICAL MONOGRAPHS [382 


nities are those of the heavily wooded belt of coniferous forest from which 
the steep-walled upper slopes abruptly rise and the alpine plateau itself. 

It is not to be understood that any distinction can be drawn, separating 
the animals of one taxonomic group ecologically from those of other groups 
inhabiting the same area; we cannot speak of ‘‘vertebrate associations.” 
On the contrary the community, as a biotic unit, must be considered as 
made up not only of all the animals but of all the plants of a habitat, 
and even these organisms present important relations with the physical 
environment, as well as with each other. But when it happens, as in the 
present case, that a group of animals ranges indifferently over a series of 
associes, to the individual stages of which certain other animals are more 
closely confined, it would seem to make for brevity and even for unity 
to discuss them as a unit in their relations to the entire diversified series 
of habitats over which they range. This is in agreement with the usage 
of plant ecologists (Clements, 1916), who consider that a formation, such 
as the coniferous forest (climax) which we are considering, is composed 
not only of the areas dominated by climax species but also of areas domi- 
nated by subclimax species; in this sense, the subclimax rock, tundra 
and krummholz stages are a part of the formation. It is interesting to 
see that the larger animals of the tundra are almost identical with those 
of the climax forest. It suggests that the larger animals, especially but 
not wholly vertebrates, use the subclimax area as a part of the formation, 
in accordance with the conception stated above. A similar condition has 
been suggested (Shelford, 1913) for the relations of some of the larger 
animals, especially mammals, to the various subclimax stages of deciduous 
forest. 

So far as known, amphibians and reptiles do not occur on the upper 
slopes. The long distance from suitable breeding-places is probably the 
reason for the absence of the former, which, as will be seen, are fairly 
abundant in various places lower down. 

Small birds appear not to frequent such unprotected places as the 
plateau of Ktaadn, despite the fact that there is abundant food in the. 
form of numerous insects and fruits of the thick-growing ericads, especially 
blueberries and cranberries, but also Cornus canaednsis, bearberry, and 
other fruits. Comparing the tables (Table IV, V) the marked absence 
of small passeriform birds will be very evident. Two forms, the junco 
and the white-throated sparrow, do occur, but they are exceptions among 
a much larger number of small birds that stay behind in the lower forest. 
Of the few birds listed, a large proportion are raptorial. The goodly popu- 
lation of small mammals of the upper regions, coupled with the fact that 
they are perhaps more easily seen and captured on the open tundra than 
in the thick lower forest, may account for this. Besides, these birds are 
powerful in flight and able to maintain themselves in the constant high 
winds as the smaller species are unable to do. They hunt over the lower 


383] A COMPARISON OF ANIMAL COMMUNITIES—BLAKE 19 


forest, however, as well. The grouse is probably a visitor, coming to feed 
on the abundant fruits of the heath plants. 

Considering the mammals of the mountain (TablesII, IIT) we find that 
a larger number of species is listed from the tundra and krummholz 
than is listed solely from the climax forest. Of course, it should not be 
overlooked that the list is actually much smaller for the tundra, since 
all the forms found there, or almost all, are found also in the spruce-fir 
forest. But if we should strike out from Table III the species which are 
largely associated with the local, waterside communities,such as pond- and 
stream side animals, we see that the proportion of forest-dwelling mammals 
that range more or less freely out onto the tundra is even larger than 
that suggested by the lists as they stand. 

Adams (1920), in speaking of Mount Marcy, says ‘‘No evidence of 
permanent residents among vertebrate life were found by us in the alpine 
area.” He quotes Batchelder (1896 and correspondence) however, on 
the presence of several species of mice and shrews. 

Of the mammals listed for the upper stations of Mount Ktaadn, 
three, the white-footed mouse, the red-backed mouse and the short- 
tailed shrew, live as summer residents, at least, on the open tundra among 
the piled rocks and alpine turf. The red squirrel is a frequent visitor in these 
areas, but his true alpine home is among the krummbholz, as might be ex- 
pected, and the same is no doubt true to a less extent for the porcupine, 
which appears to den indifferently, in summer at least, “in the fir scrub 
and rock heaps’’( Dutcher, 1903). The varying hare appears more abundant, 
to judge from the “‘sign,” in the krummholz, but it too appears to occupy 
the tundra to some extent, since Dutcher took it ‘‘on the tableland.”’ 
He gives the masked shrew only as a krummholz animal, whereas from 
the report of Batchelder it probably could be found by extensive search 
on the tundra. 

The case of the bog-lemming is of some interest. Dutcher, in 1902, 
found the whole mountain top showing abundant old microtine sign, but 
was able in extended trapping to take only two specimens, which were 
taken from the krummholz. In 1923, the writer found the evidences of 
a large colony of microtines on the grassy tundra of the tableland, just 
below the summit, consisting of characteristic holes, run-ways and grass- 
cuttings. Extensive trapping failed to take a single specimen here or in 
other localities, and the work appeared to be old and disused, but prob- 
ably, from its appearance, had been occupied at least during the pre- 
ceding summer. Two other points are of significance in this connection. 
Dutcher, in two months trapping with about ninety traps, covering all 
the typical areas of the mountain, took only nine specimens of the white- 
footed mouse, and states that they are not abundant. On the other hand, 
he does not mention the red-backed mouse as occurring on the upper 
slopes at all. The writer found, in 1923, that these last two animals were 


20 ILLINOIS BIOLOGICAL MONOGRAPHS [384 


very abundant at all levels, and especially at the upper stations. These 
facts are suggestive, if no more, in the light of work that has been done 
in this country and abroad on cyclic fluctuation in the numbers of mice 
and other animals in a given locality (Elton, 1924; Howell, 1923; Seton, 
1920). These authors suggest a periodical fluctuation in numbers of 
many animals, to be explained, in part at least, by cyclic climatic changes, 
and for some species of mice a 10-11 years cycle has been proven (Elton). 
Nothing is known of the climatic conditions on Ktaadn or the other New 
England mountains during the years 1902-1923 inclusive; but the markedly 
different findings of Dutcher and the author, using the same methods 
of study on two species occupying the same area, suggest a similar rhythm 
of increase and decrease for these two species. It is known that several 
species in a given area may thus increase and decrease together, or within 
a year of each other. These things suggest also the value of observation 
being carried on in alpine areas through a series of years, if this could 
be done for a single locality. 

The carnivores of the upper stations of Ktaadn are three in number, 
as reported. Nothing is known of their abundance there, although the 
guides report the foxes fairly common in winter, while the lynx has been 
reported as a winter visitor. The small brown weasel was taken by Dutcher 
in the krummholz, but since he says it is abundant at all altitudes, it 
must be found also in the upper tundra regions where it would find a rich 
prey among the teeming rodent population. The larger carnivores, es- 
pecially in winter, probably feed extensively on the varying hare. 

The most interesting animal of the Ktaadn tundra, now no longer 
found there, was the woodland caribou. Up to about twenty-five years 
ago, the winter feeding grounds of these animals were the tundra areas 
whose mosses and ericads, cleared of snow by the winds, furnished an 
abundant pasturage. About that time the herds were slaughtered or driven 
off, and the survivors no longer visit the mountain or indeed the state. 
Harvey says that the caribou herds came ‘from the north” and Dutcher 
that there had been “two migrations of caribou from Northern Maine,” 
the last within six years of his visit. On the other hand, Mr. Dudley told 
the writer that the migration to and from the mountain was annual, the 
animals passing the summer in the bog-forest which covers so much of 
the adjoining area, and is interrupted by more open boggy areas. No 
doubt the first two statements apply to general migrations by which at 
varying intervals the numbers of these animals were increased in the whole 
region, while the last refers to local seasonal migrations. Ecologically 
the caribou is of interest as a typical tundra animal which, living in the 
forest, has as far as possible maintained its tundra habits, clinging to the 
scanty areas of low and high tundra that break the great expanse of ever- 
green woods. 


385] A COMPARISON OF ANIMAL COMMUNITIES—BLAKE 21 


Considering the tundra vertebrates as a group, both in their biotic 
and physical environmental conditions, we may say that with one impor- 
tant exception, the caribou, they are a group of coniferous forest animals 
which have made themselves at home in the earlier successional stages 
of that habitat. For certain of the lower forms this was impossible, either 
because of breeding habits restricted to water or for other reasons; thus 
we find no amphibians nor (s. f. a. k.) reptiles in the upper regions. For 
animals that can bear the more stressful climatic conditions of the upper 
areas, the higher stations furnish a region of abundant food supply, pro- 
bably more so than is found in the forest itself, considered as a whole. 
For certain types of animals, especially those that can take refuge in rocks 
and stunted scrub, the tundra or krummbholz or both furnish entirely 
adequate shelter and materials for abode. Thus we find a very large 
percentage of the woods mammals, especially the smaller species, habit- 
ually occupying the tundra and krummholz stages as well. A considerable 
number live entirely on the tundra; to this group belong the white-footed 
mouse, short-tailed shrew, red-backed mouse and probably masked shrew 
and weasel. Another group makes its abode in the krummholz and feeds on 
the tundra; here belong the red squirrel and varying hare, and perhaps the 
porcupine. Still a third group, while making its headquarters in the spruce- 
fir forest, are temporary residents of krummholz and tundra; these are the 
red fox and Canada lynx, and perhaps the woodchuck, concerning whose 
occurrence at the upper stations, however, little is known. The caribou 
and probably the bog-lemming are, on the other hand, true tundra animals. 

If we now compare the number of forest birds found in the upper 
stations with the number of forest mammals found there, we see at once 
that the proportion is much smaller, and only a very few of the smaller 
species are found, of which the hardy junco may be named. As far as at 
present reported, about one-half of the forest species occurring also on 
the tundra are strong-winged raptorial forms, and if we omit the somewhat 
doubtful occurrence of the ruffed grouse in considerable numbers, more 
than half. The relative absence of small birds as compared with small 
mammals is particularly striking. The food supply, as has already been 
suggested and as will be seen more clearly when the invertebrates and 
plants are considered in detail, is probably more abundant on the tundra 
and equally abundant in the krummholz, as in the climax itself. The mater- 
ials for abode, the importance of which was suggested by Shelford (1913), 
must be equally well supplied by the krummholz. There is no reason to con- 
sider enemies more abundant; indeed there is some evidence, based on vari- 
ous carnivores which do not reach the upper stations, that they are less so. 

Shelford (1914) has shown that among stream animals the communities 
may be divided on the basis of extent and nature of response to varying 
strengths of current, which is the dominant physical factor in that habitat. 


22 ILLINOIS BIOLOGICAL MONOGRAPHS [386 


There seems to be considerable evidence that wind is one of the dominant 
physical factors in mountain climates in general, as will be recalled in 
connection with what was said concerning air movement under the cli- 
matic environment. There is a huge literature on the effect of this factor 
on the growth-form of alpine plants, where the results are very marked; 
this has been treated for Ktaadn by Harvey. Animals, on the other hand, 
adapt by functional response or mores (Shelford) rather than by structural 
changes. This seems suggestive that the restriction of small birds largely 
to the forest itself, while the small mammals are equally or more abundant 
on the upper slopes, may be a response to the physical factor of air move- 
ment, which thus acts as a restrictive factor in the local distribution of 
these animals. In this connection it may be said that there appears to 
be some evidence of the action of this factor on the distribution and re- 
sponse of certain Ktaadn insect types, as will be seen later. 


Pardosa groenlandica (Rock) Associes 


As a type area for study of pioneer animal conditions, a station, to be 
known in this discussion hereafter as Station A, was established on the 
northern slope of the mountain, at an elevation of 4,800 feet and studies 
made here were supplemented by other studies made in similar habitats. 
This area, which has been fully described from a geological standpoint by 
Smith and Sweet (1924) was several acres in extent, large enough to be 
typical of much biologically similar territory in the upper areas. The 
surface consists of small rocks, partly rounded by the processes of weather 
ing and attrition, interspersed with some larger ones and with a few large 
boulders scattered here and there. ‘The surfaces of the rocks, large and 
small, are largely covered with crustaceous lichens, and to these and to 
some foliaceous forms and some lithophytic mosses the vegetation is 
chiefly limited. These plants are characterized as pioneers by their inde- 
pendence of other forms of life, either plant or animal. A slight invasion of 
alpine tundra has occurred in the form of isolated islands, small in extent, 
among which the growth of deer-hair (Scirpus caespitosus) is most conspicu- 
ous. The characteristic plants are the crustaceous lichen Buellia geograph- 
ica, which is the most abundant plant; the foliaceous lichen Umbilicaria; 
and the mosses Andreaea petrophila, Rhacomitrium sudeticum and R. 
acidulare. This is an area of considerable slope and rapid drainage has not 
permitted the retention of much water or of the granitic fragments of 
erosion which are the forerunners of soil. It is also an area of great exposure 
to the high winds and of great temperature variations within short dis- 
tances (Smith and Sweet). 

Important effects may be accorded to certain animals of the rock area, 
whose influence on the scant granitic soil produced by the erosion of the 
rocks, must be similar to those mentioned above as produced by tiger- 


387] A COMPARISON OF ANIMAL COMMUNITIES—BLAKE 23 


beetles and digger-wasps on lake beaches (Shelford, 1913). Judged by 
these standards the influent animals of the Pardosa groenlandica (Rock) 
Associes are: Pardosa groenlandica (Th.), Lephihyphantes sp., Epeira 
carbonaria L. Koch, and possibly Caecilius sp., the last, however, being 
a resident phytophagous form. 

Certain other forms are predominant to the extent of being con- 
spicuous from numbers, and hence giving a characteristic aspect to the 
associes. These have a less direct effect on the habitat, and some of the 
more conspicuous are undoubtedly wind-blown from adjacent habitats. 
Such forms are not important, and their influence on the habitat is dis- 
tinctly lesser. They are therefore called subinfluents. Here may be listed 
Circotettix verruculatus (Kby.) and U pis ceramboides (L.), together with cer- 
tain cicadellids and aphids. 

This animal population is hardly more varied than the plants, but very 
interesting in its relationships. An examination of the lists of species (of 
which only characteristic predominants are given above) shows them to be 
made up of two distinct elements, local animals characteristic of the area, 
and winged visitors coming or blown from adjacent communities. These, in 
turn, are divided into two groups, phytophagous and carnivorous. The phy- 
tophagous animals which are at home in this community appear to be: 
first, the psocids, which, with their cocoons, were common on the under- 
sides of rock, where they breed. They are lichen-feeders, and must find 
abundant food. The snapping locust is given by Morse (1921) as a form 
partial to such areas. Probably most or all of the other phytophagous 
forms are true inhabitants of adjacent tundra or krummholz areas. The 
spiders form an interesting group in this associes. The webs of Lephthy- 
phantes are found in rock crevices, protected from the winds. Of Epeira 
carbonaria Emerton (1914) says that it makes ‘‘a round web between the 
stones which it closely matches in color, and among which it falls at the 
slightest jar.’’ The large Pardosa groenlandica is a true inhabitant of this 
rock region and, like the last named species, is very sensitive to footfalls 
on the rocks, disappearing into crevices when disturbed. 

It will be seen that the animal population which lives as permanent 
residents in this pioneer stage is represented by few species. The native 
phytophagous animals could hardly supply food for the several species 
of predaceous forms, but a continual stream of visitors (perhaps blown) from 
the neighboring more richly populated areas seems to supply their needs. 


Deltocephalus (Sedge) Associes 


Unforested area, apart from rock surfaces, occupies a large extent 
of the upper fifth of Ktaadn, and shows several aspects. Its alpine nature 
is indicated by the presence of Dispensia lapponica, Rhododendron lappon- 
icum, Salix uva-ursi and Arctostaphylos alpina, all found frequently in 
exposed situations. 


24 ILLINOIS BIOLOGICAL MONOGRAPHS [388 


Early stages in tundra development appear in many places where 
soil, beginning to accumulate among boulders, is able to support fructicose 
lichens, such as Cladonia, mosses and liverworts such as Bazzania trilobata. 

For the study of these conditions a station was established on the 
alpine tundra of the tableland below the summit, at an elevation of 5,060 
feet (Fig. 1). Two pioneers among vascular plants, Scirpus caespitosus 
and Arenaria groenlandica, which appear at the earlier stages, have largely 
disappeared with the increasing acidity of the raw humus which develops 
from vegetation under low summer temperatures. Various sedges and 
grasses have formed a definite turf. Xerophytic mosses also are frequent, 
a few lycopods, and Potentilla tridentata. Less commonly occur Prenanthes 
nanus, P. Bootii and Solidago macrophylla. In this stage of tundra develop- 
ment a very large proportion of the plants are cryptogamic or anemophilous. 
To the latter the high winds are decidedly beneficial in transportation of 
pollen and seeds. Of the forms enumerated only Arenaria, Potentilla and— 
for pollination only—the less frequent Prenanthes and Solidago are 
dependent on animals. ‘ 

For the purposes of this discussion, it will not be wise to attempt 
a detailed division of the plant associes of the early and late tundra series. 
Abundant lichens are: Cestraria islandica, Cladonia rangiferina and 
C. alpestris. Polytrichum is present in several species. Lycopodium Selago 
is conspicuous in rock crevices. Dominant tundra forms are Juncus 
trifidus, Deschampsia flexuosa, Scirpus caespitosus, and the flowering 
plants Arenaria groenlandica, Potentilla tridentata, and Solidago cutlert. 
Subdominant species include Hierochloe alpina, Carex brunnescens and 
C. rigida Bigelowii. Diapensia lapponica and mats of Salix uva-urst, 
S. herbacea and Arctostaphylos alpina occupy considerable areas. In the 
later stages of tundra development Vaccinium uliginosum and Vitis- 
Idaea minus dominate, while Kalmia polifolia, K. angustifolia and Ledum 
groenlandicum constitute extensive stands in many places. 

Turning now to the animal associes of the tundra, and to Station C 
in particular, the increase in number of species of animals over plants 
in this first step of succession is greatly marked, and considering that 
the plant list is probably much more nearly complete than the lists of 
animals, this fact is even more striking. A large number of groups are 
represented, and animals of all habits of life, phytophagous, predaceous, 
and parasitic. This associes, much more than was the case with the pre- 
ceding one, is a self-sufficing unit, a literal microcosm (Forbes, -1887). 
It might almost be said that, whereas a scarce, little varied biota existed 
on the rock areas, the increase of plant variety by arithmetic ratio on the 
early tundra had been accompanied by an increase of animal variety 
in algebraic ratio. The selection of predominants is rather difficult, 
since probably no single species dominates the habitat as, for example, 


389] A COMPARISON OF ANIMAL COMMUNITIES—BLAKE 25 


some plants dominate their habitats. But the most numerous animals, 
which by their numbers probably produce the maximum animal effect 
on the habitat, are undoubtedly the cicadellids, which are present in 
large numbers and some variety. There is besides a considerable popu- 
lation of other phytophaga, among which certain aphids are noticeable, 
but neither for numbers nor variety do they approach the leaf-hoppers. 
of which a number of undetermined species have been noted. 

Animal subinfluents, exerting a degree of influence on the sessile 
plant dominants by eating foliage, or affecting the numbers of phytophaga 
by preying on them are, in part: Deltocephalus pulicaris Fall., Cymus luridus 
Stal., Aphis sp., Epeira displicata Hentz., Pardosa muscicola Emerton. 

Subinfluents, generally less numerous and exerting influence to a 
lesser degree are: Macrosiphum pisi Kalt., Psylla sp., Elasmostethus 
cruciatus (Say), Rhopalosiphum sp., Phaeogenes hemiteloides Ashm., 
Acidota crenata (Fab.). 

Predominants, present in such numbers as to be conspicuous, but 
whose relations to the biota of this associes are not sufficiently well known 
to admit of more detailed ecological classification, are: Coenosia ni- 
grescens Stein., Mitopus morio Fab., Acropiesta sp., Micropterys mon- 
tinus (Packard), Clepstporthus assiduous (Cress.). Of less importance 
appear Megaselia rufipes Meig., Schoenomyia litorella Fall., Asaphes ameri- 
cana Gir., Salpingus virescenes Lec., Epurea sp., Aenoplex betulaecola 
Ashm. 

It will be seen that a considerable number of predaceous forms feed 
on the plant-eaters. Among these the Pardosas are most abundant. 
Other spiders and nabids are also present, and a large number of para- 
sitic Hymenoptera. The only strata are ground and herb, but charac- 
teristic ground-dwelling animals were less abundant than herb-living 
forms. Only two species of ground-beetles were taken, one in the larval 
stage, and two staphylinids. A careful search for animals dwelling in 
the ground was very scantily rewarded. During the summer apparently 
most of the animals of the shallow soil leave it for life on the surface. 


Cymus discors (Sedge-Heath) Associes 

Representing transition between the life of the early and late stages of 
tundra animal communities, an area, to be known hereafter in this dis- 
cussion as Station C-2, was selected. This was near the summit and 
consisted of mixed patches of grassy tundra, intermixed with heath plants, 
the latter representing the later condition of tundra. This area, as well as 
others similar to it, was examined by the usual methods of collecting and 
study. 

Subinfluents: Cymus discors Horv., Lygus pabulinus (L.), Hyperaspis 
bigeminata (Rand.), Amblyteles promptus (Cress.),Melanoplus femur-rubrum 


26 ILLINOIS BIOLOGICAL MONOGRAPHS [390 


(DeG.), Macrosiphum sp., Meadorus lateralis (Say), Calophis sp., Eucer- 
aphis sp., Elater moerens Lec., Crepidodera helxines Lec. 

Subinfluents (less numerous than those listed above): Melanoplus 
mexicanus atlanis (Riley), Botanobia frit L. var., Winthemia 4-pustulata 
Fab., Bothriothorax novaboracensis Howard, Spilocryptus cimbivorus 
Cush. 

Predominants (prominent in the associes aspect): Coenosia flavicoxa 
Stein., Hypocera clavata Lowe., Scatella lugens Lw., Phora aterrima Meig., 
Melanochelia tetrachaeta Mall., Berycyntus sp., Thanasimus dubius (Fab.), 
Perilampus stygicus Prov. These are listed in approximate order of abun- 
dance. 

Judging from the collections, it appeared that the predominant (in 
the general sense) animals were in about the same variety as in the sedge 
tundra. The more varied plants support an extensive population of phy- 
tophaga, among which no single group seems to stand out with the promi- 
nence of the cicadellids in the last associes. The red-legged grass-hopper 
is a common form and is listed among the subinfluent species, since it 
is present in sufficient numbers to influence the habitat through its feed- 
ing on the foliage. Stink-bugs, leaf-bugs, four species of click-beetles, 
two of leaf-beetles and two of sawflies feed on the plants. There is some 
evidence, however, that the animal associes revolves about the various 
aphids, which are present in considerable numbers. There are several 
genera and probably several additional species, sufficiently numerous 
to be very prominent in collections taken by sweeping among the heath 
plants. The number and character of the predaceous forms taken is 
also in accord with the conception of aphid predominance among the ani- 
mals. Six species of ladybugs, one of which, Hyperaspis bigeminata 
(Rand.), should be assigned the status of an animal predominant, the 
neuropteran Leuctra and a number of parasitic Hymenoptera, including 
braconids and ceraphronids, have been collected from this community; 
these are all known to prey on aphids either in the adult or larval stage 
or both. The ground-beetle Amara was taken running on the ground, 
and seems to be rather characteristic, the various Diptera less so. Midges, 
fungus-gnats, syrphids, hump-backed flies and anthomyiids are constant 
here, and the last two are possibly to be considered as numerical sub- 
influents. 


Pardosa uncata (Heath) Associes 


The heaths mark the climax in tundra vegetation. Plant distribution 
is very irregular. Previous note has been made of a few species characteris- 
tic of locations of great exposure and thin soil, such as Diapensia, Lapland 
rhodora and alpine bear-berry. Many more species are found in slightly 
more favorable conditions. Vaccinium uliginosum is the plant dominant 


391] A COMPARISON OF ANIMAL COMMUNITIES—BLAKE 27 


in large areas. V. pennsylvanicum angustifolium, Kalmia polifolia, and 
K. angustifolium, each have areas over which they are respectively domin- 
ant. Vaccinium Vitis-Idaea minus, Empetrum nigrum, and Ledum groen- 
landicum are very abundant. Here, of course, pollination is dependent 
on insect life, which will be seen to be sufficiently abundant. The fruits 
of the ericads, as in the preceding stage, furnish a very considerable food 
supply. 

Subinfluents: Pardosa uncata Thorell, Mecostethus lineatus (Scud- 
der)!, Athysanus arctostaphyli Ball?, Athysanus elongatus Osborn,? Platyme- 
topius acutus (Say)*, Anatis 15-punctata (Oliv.), Coccinella transverso- 
guttata Fald. 

Subinfluents (less numerous than the above): Pheletes sp., Chloro- 
pisca glabra Meig., Formica sanguinea var. Only a small collection of 
animals was taken from this station, of which the predominant species 
are listed, together with a considerable number of records taken from the 
literature on this or similar areas of the mountain. Predominant animals 
appear to be cicadellids of several species, with the spider Pardosa uncata. 
Athysanus arctostaphyli and A. elongatus are particularly characteristic 
as feeding on the dominant plants. In the ground was taken Pheletes 
larvae and under loose stones the ant Formica sanguinea var. Two species 
of coccinellids no doubt feed on small insects that infest the dominant 
plants. The fly Chloropisca belongs to a family largely characteristic 
of meadows and is perhaps an immigrant—or blown in—from the grassy 
tundra. 


Linyphia nearctica (Krummholz) Associes 


Where slight depressions in the expanse of the tundra have accumulated 
sufficient humus and offered initial protection from wind, fir and spruce 
have developed as definite islands. These two forms, Picea mariana and 
Abies balsamea, in separate stands, cover large areas on the saddle and the 
slopes above. So closely do the individual trees grow that it is difficult 
to force a passage through them (Fig. 2). The extreme stature is attained 
at the most western point of the “saddle” (Harvey, 1903a), where the 
trees approximate ten feet. Here then, as over the entire mountain and in 
the lowland of the immediate vicinity, the climax plant stage is Picea- 
Abies forest. 

The shade of the close-growing trees is so thick that in many places 
there is practically no forest floor vegetation. Where mosses appear, a 
means of retaining moisture is furnished. In such a situation the death 
of a tree offers a wind-protected, well-watered opening. Such a spot 
becomes populated with plant species characteristic of openings in the 


1Morse (1921). 
2Osborn (1915). 


28 ILLINOIS BIOLOGICAL MONOGRAPHS [392 


coniferous forest at lower levels. Amelanchier oligocarpa is fairly common. 
Although seasonal societies are not sharply differentiated as a rule, on 
account of the low temperatures that persist throughout the summer, 
Linnaea borelis var. americana is conspicuous only in June. The most 
abundant species growing on the forest floor are Chiogenes his pidula, 
Oxalis acetosella, Cornus canadensis and Trientalis americana. Associ- 
ated with them are Clintonia borealis, Maianthemum canadense, Coptis 
trifolia and Streptopus roseus. 

The low-growing trees, twisted close to the ground, which consti- 
tute krummholz, offer protection to small mammals such as squirrels 
and hares. They present mechanical obstructions against pursuers, 
whether cursorial mammals or raptorial birds. Their dense shade and the 
continuous evaporation from the moss about their roots afford equable 
atmospheric conditions in contrast with the rapid fluctuations of these and 
other climatic factors in more exposed parts of the mountain. If the fruits, 
leaves, bark and roots of the immediate stand do not furnish suffificient 
food, plenty can be obtained among the heaths of the adjacent tundra. 

Subinfluents: Podisma glacialis (Scudder)!, Gnathosa brumalis Th., 
Theridion szelotypum Emerton®, Epeira displicata Hentz, Notolophus 
antiqua L, (juvenile), Linyphia nearctica Banks.? 

Subinfluents (less numerous than the above): WNeuratelia scitula 
Johannsen, Cystoma pilipes Lw., Lycosa sp., Scatophaga furcata Say. 
The last named could be perhaps best considered as a dominule or sub- 
dominule, frequenting the microhabitats supplied by decaying fecal or 
other organic matter. They are by no means confined to this associes. 

The krummbholz vertebrates have already been considered. The 
invertebrates have been less studied than those of some of the other 
associes; collections made include the forms given. Particularly charac- 
teristic are the spiders; Gnathosa was taken under stones and in the thick 
moss, in which it habitually occurs. Two species are listed by Emerton 
(1920) as particularly characteristic; it will be seen that these, together 
with a young Epeira which the writer found very abundant, are both 
spinners. Theridion selotypum, according to Emerton, “spins large, 
coarse webs between the spruce branches, with nests in which the female 
and her brood of young live.”’ Linyphia nearctica is also found on spruce. 
The irregular, delicate strands of the young Epeiras were found by the 
writer on a warm August day abundantly stretched between the tips and 
branches of the semi-prostrate, breast-high conifers. The krummbholz 
thus is seen to furnish the first habitat in succession which supplies favor- 
able conditions for any general and varied population of spinners, the few 
species of this habit found heretofore being confined to spaces between 


1Morse (1921). 
2Fmerton (1914). 


393] A COMPARISON OF ANIMAL COMMUNITIES—BLAKE 29 


rocks or among low heath plants and grasses. Among the krummholz, 
on the other hand, the branches of the alpine trees furnish a place for 
attachment of webs, while the thickness of the growth to some extent 
protects them from the force of the excessively strong winds. 

On the forest floor, we find besides Gnathosa brumalis, two lycosids. 
one of which was fairly abundant. 

Thus we see in the krummholz, as illustrated by the spiders, for the 
first time occurring a definite stratification of animals into societies, a thing 
not possible in the earlier biotic associes, with their shallow soils and 
low herb cover. 

Another characteristic animal of this community is the White Mountain 
wingless locust (Podismalacialis). 

Fungus-gnats (Neuraielia scitula) and dance-flies (Cystoma pilipes) 
are abundant under the dense shade of the scrub, where conditions for 
the former are particularly suitable. Two species of anthomyiids and 
two of sapromyzids were taken, and their larvae no doubt feed on the 
abundant decaying vegetable matter. The caterpillars of Notolophus 
antiqua were taken, one of the few Lepidoptera taken or observed in 
the upper stations, whose high rate of air movement is perhaps less suit- 
able for insects of this character. Among the Hymenoptera are Ich- 
neumonidae, Belytidae and Scelionidae; the second are known to para- 
sitize dipterous larvae. 


Rheumaptera hastata (Upper forest) Association 

A small collection of animals was made in the upper regions of the 
climax forest, between Chimney Pond (2,900 feet) and the foot of the steep 
slide leading up to the plateau and upper stations. The plants are similar 
to those described below for Station E; this upper climax forest will be 
known as E-2. The invertebrates taken are listed. 

Subinfluents (probably none affecting directly the true sessile domi- 
nants): Rheumaptera hastata L., Argynnis atlantis Edw., Malacosoma 
disstria Hon. (juvenile), Hepialus mustelinus Pack., Acronycta sp. (juve- 
nile), Psocus sp., Platynus sinuatus (Dej.), Galerucella cavicollis (Lec.), 
Coccinella sp. (juvenile), Simulium venustum Say. 

Here psocids were abundant, feeding on lichens. The ground beetle 
Platynus sinuatus was taken among stones and mosses on the ground, 
and the leaf-beetle Galerucella cavicollis. On the forest floor occurred the 
larva of one of the coccinellids. Three species of Lepidoptera were tak- 
en from this station, the spear-marked black (Rheumaptera hastata), 
swift (Hepialus mustelinus) and a dagger (Acronycta). The number 
of these and other Lepidoptera in the climax forest, as contrasted with the 
great scarcity of this order at the upper stations, suggests that, as in the 
case of the birds, air movement may be a factor in their local distribution. 


30 ILLINOIS BIOLOGICAL MONOGRAPHS (394 


This is almost certainly the case with species like the swifts, which even 
in the forest do not appear to fly usually at any great height. The spear- 
marked black was an abundant species throughout the lower forest, but 
was not observed or taken at any of the upper stations. 


Sciurus hudsonicus (Spruce-Fir) Association 


The studies were mostly made in the climax Picea-Abies forest of the 
South Basin at Basin Pond. The elevation was 2,400 feet, high enough to 
illustrate the biota of the mountain sides up to the level of the slides. The 
station, known as Station E, was situated on a moraine ridge a few rods 
back from the swampy shore of the pond; in some places Thuja ran to the 
edge of the water. In other spots a strip of Chamaedaphne intervened. 
The ridge itself consisted of a soil of decomposing Spagnum, from which 
projected glacial boulders and partly buried rocks. The characteristic 
plants were Picea and the abundant and profusely-blooming Kalmia 
angustifolia, Viburnum cassinoides, Amelanchier oligocarpa and Nemo- 
panthus mucronata. 

From the plant standpoint, this region is the most mesophytic under 
consideration in this study. While Basin Pond itself is swept by heavy 
winds, the surrounding forest offers to animal life ample protection from 
storms. Food is abundant in berries, seeds, bark and leaves of many 
kinds. Inaccessibility for human beings may be mentioned as another 
factor making for seclusion, of importance particularly to the larger 
animals. As has already been discussed in detail, practically all the verte- 
brate life in general, and the bird life in particular, center in this part 
of the mountain. 

Subinfluents: Serropalpus barbatus (Schall.), Agelena naevia Walc- 
kenaer, Amaurobius sylvestris Emerton, Epeira trivittata Keyserling, 
Zilla montana Koch, Syrphus torvus O. S. : 

Subinfluents (less numerous than the above): Mesopsocus unipunc- 
tatus Miill., Pogonocherus penicellatus LeC., Papilio turnus L., Eupeth- 
icia sp., Leptomeris inductata Gn.? (juv.), Olethreutes sp., Colias philo- 
dice Godt., Sarcophaga aldrichi Parker. (Perhaps the last named should 
be classed as a dominule, whose true ecological position is that of a pre- 
dominant in the microhabitat furnished by the decaying body of a dead 
animal), 

Predominants (conspicuous in the habitat, but not further classified 
ecologically): Fannia canicularis L., Chrysops sordida O. S., Camponotus 
h. p. ferrugineus Fabr., Aedes fitchii Felt, Culiseta impatiens Wlk., Platyura 
subterminalis Say, Prosimulium hirtipes Fries., Chrysops niger Macq., 
Tabanus astutus O. S. var., Xylota curvipes Loew., Tinea sp. 

The invertebrates listed are those more prominent in the collections 
and records. Faunistically they form a rather interesting combination 


395] A COMPARISON OF ANIMAL COMMUNITIES—BLAKE 31 


of alpine and sub-alpine forms with species widely distributed at lower 
levels. Ecologically the invertebrate predominants appear to be spiders 
of eight genera and eleven species. There are also two species of ground- 
dwelling phalangids and two of ground-dwelling mites, so that the arach- 
nid population of the forest floor of this associes is very large and varied. 
Many live on the mossy ground under the thickly growing conifers and 
among the crevices of the numerous rocks. In such places are found the 
rough webs of Amaurobius. In scrub, or attached to dead limbs or stubs 
at that level, we find the orb-webs of Epeira trivittata, and Agelena naevia 
builds its funnel-shaped webs among low herbs in openings in the forest. 
Among the low trees are found the imperfect orbs of Zilla montana. The 
distinct stratification of the spiders, especially the relatively large numbers 
of ground dwelling-forms, is of interest. One of the dominant physical 
factors in this as in the other mountain habitats is the strong wind. It 
is certain that the spinners of erect orbs are at a disadvantage in such 
conditions, as compared with those which either run down their prey like 
the Lycosas or build low, little-exposed webs like Amaurobius and Agelena. 
It was observed that the webs of Epeira were soon torn to pieces by the 
wind. 

The insect population is large, both in individuals and species and 
only certain species will be given particular discussion. In openings 
of the forest the Locustidae were abundant; the two-striped locust, the 
northern locust and the banded locust all being taken near the forest 
margins of artificial clearings; none of these are forest species. Partic- 
ularly characteristic of such moist forest conditions are the two Cica- 
dellidae, Deltocephalus sylvestris and Graphocephala coccinea, found feed- 
ing on many plants of the lower forest strata. In the ground-stratum 
was found the staphylinid Antobium pothos and the larva of a cephalooid. 
A number of other beetles were collected, of which the most characteris- 
tic appeared to be the cerambycid Pogonocherus. In this moist forest 
station Diptera were very abundant. Tipulidae were common, three 
genera and species being represented. Four families, whose relations to 
man are such as to bring their activities much to his attention were un- 
fortunately prominent in the community: the Culicidae were represented 
by Aedes fitchii and Culiseta impatiens; the Tabanidae by two species 
of Chrysops and one of Tabanus; the Simuliidae by Prosimulium hir- 
tipes; and the Muscidae by Musca domestica. The last named was a man- 
brought importation due to lumbering operations, but the others are 
typical and numerous in the natural habitat. Here were found two syr- 
phids, Syrphus torvus and Xylota curvipes, while the Myceteophilid 
Platyura subterminalis was abundant in favorable spots locally. 

The most interesting feature of the habitat was the relatively large 
number of Lepidoptera as compared with those found in the upper stations. 


32 ILLINOIS BIOLOGICAL MONOGRAPHS [396 


Eight species were collected, and probably a dozen in all were seen. Evi- 
dently the climax forest is the true montane home of this group in general 
and only hardy species or individuals can cope with the conditions of the 
open tundra, where they are never abundant. 

In general, we may say that the spruce-fir climax shows, by its animal 
as well as its plant life, that it is in part a wave of upward-pushing biota 
from the more temperate forest below, invading the lower boundary of 
the sub-alpine forest. Here we find a large number of species, showing 
a mixture of the two populations. The climax habitat shows a list of charac- 
teristic species, not found in the subclimax stages. These species of the 
climax are arranged in stratal communities or socies, although this fact 
was not particularly studied for any group except the spiders; there is 
no reason, however, to suppose that this stratification does not extend 
to the whole animal population. 


Aeschna (Pond-Bog) Associes 


Some collecting was done and the conditions were studied in a semi- 
aquatic community furnished by a pond-bog near Pamola Pond, at an 
elevation of 2,700 feet. The pond itself is a small body of water, occupying 
what is evidently an old glacial depression and held in place by the moraine 
whose glacial structure, indeed, is very plain at one point where it has been 
cut through by a ditch in aid of lumbering operations. On the eastern 
and southern sides of this pond the moraine ridge has a stunted growth of 
spruce and fir, the climax forest of the Great Basin of Ktaadn. On the 
other sides, the pond is being invaded by a regular sphagnum bog complex, 
the sphagnum mat overhanging the deep water close to the shore in spots, 
and being followed by the typical marsh shrubs, among which Chamae- 
daphne is most common; the stunted Picea-Abies forest brings up the rear, 
and the whole seems to furnish a rather typical example of the filling of a 
glacial pond by vegetation. Northwest of the pond itself, and connected 
with it by a flooded bog, is a small, shallow bog-pond, where the process 
of filling has so far advanced as to give the impression of rather a swamp 
than a pond, and some of the spruce-fir forest nearby is evidently growing 
on what was once a part of the old pond. The general environment is 
shown in the illustration (Fig. 3). 

From the standpoint of plant succession, the most significant feature 
of this small sphagnum bog is its possession of subalpine species, such as 
Empetrum nigrum and Vaccinium uliginosum, not found elsewhere until 
the high slopes above the steep ascent are reached. 

The greater number of plants are those common to sphagnum bogs 
of this latitude. The steps in development from an open pond are plain. 
Sphagnum forms the basis for Scheuchzeria palustris and Drosera follows, 
and later Sarrancenia with Vaccinium oxycoccus and Smilacina trifolia. 


397] A COMPARISON OF ANIMAL COMMUNITIES—BLAKE 33 


Carex is represented by ¢trisperma and pauciflora Kalmia is abundant, 
especially K. polifolia, on the numerous islands of soil rising slightly above 
the water. Individual trees of Picea mariana and Larix laricina, stunted 
and unhealthy looking, represent the encroachment of arboreal forms, 
frequently on small islands separated as yet from the main shore by narrow 
aisles of standing water (two or three feet deep in late August). At one 
point Thuja occidentalis appears. 

The absence of orchids, noted also for Lake Tear bog on Mount Marcy, 
is explained by Harvey as due to isolation. 

The persistence of subarctic forms completely obliterated from other 
parts of the lower slopes indicated the tremendously slow development 
of the sphagnum bog. It is, however, being gradually filled in and sur- 
mounted by sufficient humus to support mesophytic forms. Near the 
advancing trees are beginning to appear such plants as Osmunda cinna- 
monea, Cornus canadensis, Clintonia borealis, and Nemopanthus and Ame- 
lanchier oligocarpa. 

The air temperature, in the shade and just over the surface of the water 
varied from 17°C to 20°C, at 3:30 P M on afternoons in August. The 
temperature of the water, close to shore in the shade of vegetation was 
12°C at a depth of 6 inches; at the same depth, but 8 feet out from shore, 
and therefore in the sun, the temperature ranged between 13°C to 16°C. 

Subinfluents: Aeschna sp., Gerris sp., Gyrinus affinis Kby., Gyrinus 
lugens LeC., Trepobates pictus (H. S.), Lestes uncatus Kby., Epeira patag- 
tata Clerck, Coccinella trifasciata L., Leptura chrysocoma Kby., Te- 
tragnatha extensa (L.), Misumena vatia (Clerck), Philodromus sp., Lin- 
noporus rufoscutellatus Latr. (?), Hydrophorus pirata Lw., Hilara tristis 
Lw. 

Subinfluents (less numerous than the above): Misumena asperata 
Emerton, Dolomedes sexpunctatus Hentz, Notonecta sp. (juvenile), Sinea 
diadema (Fabr.), Euscelsis humidus (Osb.), Agabus discolor (Harr.), 
Hydatiscus sp. (juvenile), Mamestra sp. (juvenile), Platypalpus flaviros- 
tris Lw., Frontina sp., Hyalomyodes triangularis Lw., Vespula norwegi- 
coides Sladen, Zaglyptus incompletus (Cress.) 

Dominules (predominant in microhabitats within the associes): Aphis 
spireaphila Patch (numerous groups on scattered Spiraea), Sminthurus 
spinatus MacGillivray, Sapromyza sheldoni Coq. (on decaying organic 
matter). 

Predominants (conspicuous in the associes, but not further classified 
ecologically): Chirononmus sp., Siphlurus alternatus Say, Tanypus sp., 
Limnophilus rhombicus L., Lispocephala erythrocera Desv., Arctocorixa 
sp. (juvenile), Sciara sp., Ochthera mantis DeG., Diplotaxia versicolor Lw. 

The animal population of this area is listed above (invertebrates) 
in part only. The list does not indicate, for the animals, any number of 


34 ILLINOIS BIOLOGICAL MONOGRAPHS [398 


boreal species, though Coccinella trifasciata may be so considered (Blatch- 
ley, 1910). The habitat showed two strata, water and herb, From the 
water were taken nymphs of Arctocorixa, Notonecta Siphlurus alternatus, 
and several species of gerrids, of which one (undetermined) species appeared 
as one of the numerical predominants. The adults of Limnoporus rufo- 
scutellatus and Trepobates pictus were taken, the latter being more common; 
also larvae of a Hydatiscus and three gyrinids, G. affinis, G. lugens, and 
G. latilimbus, the first two named being predominants. Here also was 
taken the larva of the pond-lily chrysomelid, Galerucella nymphaeae, 
on the yellow lily, and a trichopterous larva Limnophilus rhombicus. 
In the damp moss and debris around the roots of the swamp-plants, 
was found the dytiscid Agabus discolor. 

The stratum of vegetation over the water yielded, to sweeping and 
individual collecting, a large and characteristic population of swamp 
animals. The webs of Tetragnatha extensa were found on dead branches 
of dwarf spruce; they contained mostly the remains of chironomids. 
The crab-spiders Misumena asperata and M. vatia were found, the latter 
living and breeding on Kalmia. Young Philodromus and specimens of 
Dolomedes sexpunctatus were also taken from the moist herbage. Emerton 
gives Epeira labyrinthea as characteristic of this habitat. 

From the vegetation was taken Sminthurus spinatus. Spiraea grow- 
ing along the edge of the bog was heavily infested with Aphis spiraea- 
phila; Lygus pabulinus was swept from the plants, as well as the cater- 
pillar of a noctuid (Mamestra). A large population of characteristic 
flies were taken in flight or resting on the swamp plants. They included 
Chironomus and Tanypus, the mycetophilid Sciara, the long-legged 
fly Hydrophorus pirata, the dance-flies Hilara tristis and Platypalpus 
flavirostris, Sapromyza sheldoni, an ephydrid, Ochthera mantis, the chloropid 
Diplotaxia versicolor, the anthomyiid Lispocephala erythrocera, and two 
tachinids, Frontina and Hyalomyodes triangularis. 

Prominent in flight over the water was the dragon-fly Aeschna, while 
the stalk-winged damsel-fly Lestes uncatus was abundant along the shores 
of both ponds. 

Other species taken in this habitat, mostly by sweeping from vegeta- 
tion, are Eucelis humidus, from the heath-plants; the spiny assassin-bug, 
Sinea diadema; an aphis, Macrosiphum: Coccinella trifasciata; an ich- 
neumon-fly, Zaglyptus incompletus; two species of saw-fly larvae; and the 
wasp Vespula norwegicoides. Here was taken the old tussock-moth, No- 
tolophus antivua. The beetle Mezium americanum was probably intro- 
duced by the establishment of the lumber camp at Basin Pond, not far 
away. 

The pond-bog community shows in general an assemblage of ani- 
mals common to such habitats at all levels and in all types of forma- 


399] A COMPARISON OF ANIMAL COMMUNITIES—BLAKE 35 


tions. It is a distinctly local habitat, composed of characteristic species 
with characteristic mores, and is to that extent ecologically distinct 
from the coniferous forest climax which surrounds it. It is no doubt 
undergoing gradual succession, as is indicated by the vegetation, to the 
climax forest; this process was not studied for the animals, the time only 
permitting a survey of the most characteristic bog conditions. Enough 
has been done to indicate that the community is distinctly a local one, 
with an animal population distinct in composition and mores from that 
of the surrounding climax, by which, no doubt, it will eventually be succeed- 
ed. 


The Steep Slide Animal Community 

A small collection of animals was made, and the conditions briefly 
noted, on a steep slide leading from the head of the South Basin up to 
the tundra of the saddle. This station was at an elevation of 3,450 feet. 
The slope, which was as steep as rocks and earth would lie, was covered 
in the lower part by washed-down granite detritus, farther up by rocks. 
Save for lichens, vegetation on the slide itself was practically absent. 
The sides, however, are being invaded by various plants, among which 
Solidago, Epilobium and Alnus may be noted, with the usual rear-guard 
of krummholz spruce. This station showed a rather curious mixture of 
animals from the extreme stages of succession in both directions. The 
dominant animal appeared to be Pardosa groenlandica, a bare rock species 
also dominant in Station A. On the other hand, this was the highest station 
for the amphibians, the common toad (Bufo americanus) being observed 
here. It is known to exist otherwise only in the climax forest, but was 
here no doubt associated with the upward extension of that forest on 
the steep slopes. The caterpillars of Malacosoma disstria were heavily 
infesting stunted birch, and the cicadellid Oncopsis was found feeding 
on alder. The former was found otherwise only at levels below this station; 
the spider Lycosa albohastata was found here, and also above on the alpine 
tundra, while the harvestman Mitopus morio and the ubiquitous humble- 
bee Bremus terricola occur both above and below; the latter appeared 
here on the goldenrod. It might be expected that these steep slopes would 
be a tension line between the animals of the upper plateau tundra and 
those of the climax forest, but it is interesting to see how well this is indi- 
cated by the presence in the same station at this level of animals as ecolog- 
ically diverse elsewhere on the mountain as Pardosa groenlandica and 
Bufo americanus. No doubt this partly explained by the fact that at this 
level the forest advances directly onto the bare area, without interven- 
ing tundra stretches that occur with the shallower soil and greater wind 
exposure of higher altitudes. 


36 ILLINOIS BIOLOGICAL MONOGRAPHS [400 


DISCUSSION AND SUMMARY 


The climate of Mount Ktaadn, as far as we have actual or inferred 
knowledge of it, is a rather typical montane climate, showing low mean 
and minimal temperatures, heavy precipitation and high winds, the last 
associated with high evaporating power of air. These factors are operative 
in all areas studied, but show a general increase with altitude and exposure. 
It is an entirely different climate from that of the low country coniferous 
forest lying around the base of the mountain and likewise entirely different 
from the climate of the tundra regions lying near sea level farther north 
(Fig. 9). Its hythergraph does not show similarity to either of these, 
although they overlap somewhat during the warmer part of the year. 
It is much cooler at all seasons of the year than the former, but never 
reaches the extremely low winter temperatures of the latter. The precipita- 
tion is greater than that of either. 

From the standpoint of both ecology and faunology, these facts seem 
significant. There are a number of species found at high altitudes on the 
northeastern mountains, which are considered as boreal or possessing 
northern affinities, that is to say, they are identical with, or more or less 
closely allied to, species living much farther north at lower elevations. 
We have generally considered that these species, of general distribution 
at low altitudes during the southern extension of the ice-sheet, found 
on the retiring of the glacial margin the same climatic conditions at high 
altitudes that occurred farther north near sea-level, and hence these 
arctic-alpine areas became refuges for groups of boreal species which were, 
as it were, left stranded on the mountain-tops. It is interesting to see 
that the conditions in these areas, as represented by the hythergraphs 
based on the Mount Washington data, appear those of a climate decidedly 
different from that of the Ungava regions. Since the species appear to 
be structurally constant in both places, there must have occurred phys- 
iological differentiation and such species are perhaps to be considered 
as physiological ones. Undoubtedly what is needed here is a study of the 
physiological life histories (Shelford, 1913) of the same species occurring 
on the high tundra of the New England mountains and the low tundra 
of the regions lying farther north. Such information is at present entirely 
lacking, but a similar phenomenon has been investigated for species of 
Cicindellidae living both in Illinois and Manitoba; in this case there 
was a distinct correlation between the life histories of these two widely 
separated groups of individuals of the same species, and the climatic 
conditions respectively operative. 

Mingled with these truly alpine animals are a number of other forms 
of general distribution in the northern coniferous forest climax at lower 
levels, or of even wider distribution, and the population is a mixture 
of these two main types. This entire population, or series of animal 


401] A COMPARISON OF ANIMAL COMMUNITIES—BLAKE 37 


communities, is involved in a process of succession, by which, as the naked 
and eroding rock at all levels is gradually becoming covered by the climax 
forest of the region, the characteristic animals of the areas involved are 
also undergoing corresponding and progressive changes. The process 
is complex, involving as it does biotic, edaphic and climatic factors, re- 
spectively operative to different degrees in the different stages and under 
various local conditions. In general it may be said to consist of the follow- 
ing successive associes, leading gradually to the animals of the climax 
forest: 

A biotic community capable of living on bare rock, in the practical 
absence of soil. The plants of such a community are chiefly lichens, 
and are independent of animals. The resident animals are forms capable 
of living on the sparse plant growth, or predaceous forms, including a 
number of highly characteristic spiders. This community is probably 
not self-supporting, from the animal side, but its predators depend in 
part for food on insects blown from adjoining regions. It is distinctly 
a one-stratum community, subterranean or rather sub-lithic, in part 
a response to the climatic factor of air movement. This has been referred 
to as the Pardosa groenlandica (Rock) Associes. 

A biotic community consisting of the turf of alpine grasses and sedges 
that come to occupy the first thin soil formed by erosion and the decay 
of previous organisms, and its animal inhabitants. This shows a consider- 
able increase in plant variety, and a more marked increase in animal 
variety, consisting of numerous phytophaga and their enemies. It appears 
to be a self-sufficing biotic community, a microcosm. It is the result 
of changes, principally physiographic but in part biotic, from the previous 
community, and is still to a large extent a one-stratum complex, the herbs 
and their inhabitants. If designated by the group of animals which are 
certainly most numerous in species and individuals, this stage would be 
called a cicadellid associes, the Deltocephalus (Sedge) Associes. 

A biotic community composed of the alpine heath-plants which thrive 
with the accumulation of a better and a deeper soil, and the associated 
animal population. This community is also self-sufficient consisting of 
a varied population of phytophagous forms and various predaceous species. 
It has been evolved from that just described by a series of changes in 
which the biotic factors have probably been progressively more important, 
the physiographic ones less so. It is difficult to fix upon animal predomi- 
nants sufficiently characteristic to be used in naming this associes, but 
the Cymus discors (Sedge-Heath) Associes has been suggested. 

A biotic community consisting of krummholz coniferous forest and 
its animal denizens. This has been produced from the preceding stages 
by a complex of factors, which are, however, probably chiefly edaphic 
and biotic, rather than climatic. The animal population is to a considerable 


38 ILLINOIS BIOLOGICAL MONOGRAPHS [402 


extent that characteristic of climax coniferous forest, but some large 
vertebrates are lacking and there are highly characteristic invertebrates. 
This is a stratified animal community, but the herb society is scanty or 
missing and the tree stratum is hardly higher, in many places than the 
shrub society of other forests. From a characteristic animal, this is called 
the Podisma glacialis (Krummholz) Associes. 

A biotic community consisting of the climax spruce-fir forest and its 
associated animals. This is a well-stratified and established formation, 
whose existence on the area it occupies will be very long under natural 
conditions. Its evolution, like that of the krummholz, has been edaphic 
and biotic, rather than climatic, but it is in itself a climatic climax. Under 
usual conditions, it would be (that is, when not subjected to attacks 
of such forms as the spruce bud-worm), difficult to name animal pre- 
dominants; indeed, no animal usually found there dominates the habitat 
as the forest itself does. But if this association is to be named after one 
of its highly characteristic animals, it could be called the Sciurus hudsonicus 
(Spruce-Fir) Association. 


CONCLUSIONS 


The animals of alpine tundra communities show a definite succession, 
beginning with the communities inhabiting bare or lichen-covered rocks, 
and passing through subclimax stages until the climax association is reached 
in the animal community of northern coniferous forest. 

This succession includes a gradual change in the animal life, especially 
as regards species; animals abundant in the earlier associes being absent 
in the later ones, and vice-versa, and the intermediate stages showing a 
more or less gradual falling off of earlier species and increase of later 
ones. ; 

The various animal tundra communities are characterized by pre- 
dominant or at least characteristic animals with different types of habits 
or mores, and these, in so far as they have been studied, show an adapta- 
tion response comparable with the structural responses of plants under 
similar conditions; this may be exemplified by the habits of the Pardosas, 
dominants of the rock animal associes, with those of the Epeiras, first 
prominent in the forest stages of succession. 

The factors influencing the transformation of the earlier associes 
of tundra are probably largely biotic and edaphic, since the climatic 
differences of the various tundra areas cannot be decisive, although they 
have not yet been measured instrumentally. There is every reason to 
suppose that the animal associes are in the.main determined by the plant 
associes, and that the reverse condition, has been important only indirectly. 
The indirect effects of the subinfluents consist at least in contributing their 
dead bodies to the enrichment of the soil. 


403] A COMPARISON OF ANIMAL COMMUNITIES—BLAKE 39 


On the other hand, the physical differences between the tundra en- 
vironments as a group and the climax and subclimax forest stages appear 
to be considerable, especially as regards air movement, and may possibly 
have exerted a decisive influence on certain animals, confining them to 
the later (forest) associations. 

The factors influencing succession over the various tundra areas have 
been only to a limited degree operative in the case of certain animals, 
especially but not exclusively bertebrates, and more especially the smaller 
mammals; such animals show less restriction to the boundaries set by 
various invertebrate and plant associes, or none at all. 


40 ILLINOIS BIOLOGICAL MONOGRAPHS [404 


ANIMAL ECOLOGY OF MAINE PINE-HEMLOCK FOREST 
SCOPE OF WORK 


Of the papers cited in the introduction as dealing in a quantitative 
way with the ecology of land animal communities, the most elaborate 
and the one covering the longest period of time is that of Weese (1924). 
This author, using recording instruments to measure the factors of the 
physical environment and the method of ‘quantitative sampling” for 
the study of the animal population, carried his work throughout the year. 
His paper presents a very complete account of the annual climatic and 
biotic cycle of the elm-maple forest where the work was done, the stratal 
and seasonal societies and their dominants, and the correlations between 
environmental changes and animal response. 

The present portion of this study gives the results of an attempt to 
apply the same method to the study of the animal ecology of northern 
coniferous forest. This was of necessity a short-time study, embracing 
the summer months of 1923, during the latter part of which the most 
extensive of the biotic studies were made. It is not therefore to any degree 
a study of seasonal societies, but it is hoped that it will give some idea of the 
stratal societies and the physical conditions existing in coniferous forest for 
comparison with those of the deciduous forest as described by Weese for the 
same period of the summer. A rather large part of the work is concerned 
with the physical conditions of the habitat. As these are little known 
it was deemed best to devote a considerable portion of the limited time 
available to their investigation and the accumulation of instrumental data 
on the subject. 

As it seemed hardly likely that the succession of climatic changes, 
through so short a period and at this time of the year, would be very mark- 
ed, particular emphasis was laid on the question of stratification of these 
conditions, and the instruments were exposed with this in view. The envi- 
ronment was investigated in terms of stratification of temperature, humid- 
ity, evaporating power of air, and light. Some of the instruments used 
not being of the recording type, recourse was had to the expedient of read- 
ing them several times a day at periods considered as critical in meteorol- 
ogy. 

The biotic data was obtained by the method described by Weese as 
sampling. It will be discussed in detail later. For the present it may be 
said that the collecting consisted in taking samples of the animal population 
of the strata where the physical factors were being instrumentally meas- 


405] A COMPARISON OF ANIMAL COMMUNITIES—BLAKE 41 


ured; the methods of taking these animal population samples were at 
all times kept uniform. It was not, however, possible to take and study 
these samples as frequently during the early part of the summer, because 
of the limitations of time imposed by other duties. For this reason the 
biotic studies for the month of August are more complete than those pre- 
ceding. 

The birds were not considered in the present study, which from the 
very nature of the collecting, chiefly concerns invertebrates. The area 
studied was trapped from time to time, however, to get some idea of the 
mammals present and their relative abundance. The results of this will be 
included in a separate portion of the discussion. The forest is too near 
cultivated areas and too much subjected to human influences, to make 
the findings on the mammalian population of more than local interest. 


ENVIRONMENT. 


The area studied is a heavy growth of white pine (Pinus strobus), Nor- 
way pine (P. resinosa) and hemlock (Tsuga canadensis), comprising a part 
of the forest under the charge of the Forestry Department of the Agri- 
cultural College of the state university at Orono, Maine. The stand con- 
sists of mature trees of large size and, while not virgin, has never been 
completely cut off, although individual trees have been taken out here 
and there. A little birch and alder occur, also a few young maples and white 
ash. The area is southeast of the university campus, and adjoins farm 
land on some of its irregular boundaries, while on others it is bounded 
by swampy land covered with young second growth deciduous forest. 
The elevation is about 115 feet, and the relief is slight, but with a little 
slope to a swampy brook in the eastern portion. 

The undergrowth is scanty; individuals or small stands of a single 
species constitute the discontinuous vegetation. The intervening ground 
is covered with a thick carpet of coniferous needles, twigs and other or- 
ganic debris. The shrub stratum is especially poorly developed. The 
number of plant species present is increased by the influence of open 
fields on two sides, south and west. The swamp and young forest on the 
northeastern boundary contribute a few forms not characteristic of the 
area as a whole. 

Relatively few species of shrubs and herbs were noted in the vicinity 
of the stations. The shrubs were Corylus rostrata, Rubus alleghaniensis, 
Lonicera canadensis, Ribes lacustre and Spiraea latifolia. The most promi- 
nent herbs were Copftis trifolia, Maianthemum canadense, Lysimachia 
quadrifolia, Aster spp., Rubus triflorus, Clintonia borealis, Solidago sp., 
Cornus canadensis and Aralia nudicaulis. 

The lowest part of the woods lies somewhat north and east of the 
station. In early summer it, comprises a swamp through which runs 


42 ILLINOIS BIOLOGICAL MONOGRAPHS [406 


a small stream. Here occur several forms not seen elsewhere. The most 
conspicuous are: Fraxinus pennsylvanica (a few young individuals), 
Cornus stolonifera, Typha latifolia, Viola sp., Onoclea sensibilis, Ranunculus 
abortivus and Galium trifidum. 

Along the borders of the coniferous forest, especially towards the north, 
the following arborescent forms appear, all as young growth: Amelanchier 
canadensis, Prunus pennsylvanica, Prunus virginiana, Prunus serotina, 
Populus grandidentata and Salix sp. 

It will be seen that many shrubs and herbs are species in general 
characteristic of northern coniferous forest. Some even appeared among 
the sub-dominants of alpine spruce-fir forest on Mount Ktaadn. The 
presence of several species, such as red clover, in this type of habitat 
can only be explained by the adjacent agricultural lands. To this extent 
is the forest atypical of untouched habitats of this type. It was, however, 
the only area available for study that even approximated natural con- 
ditions, and the interior region where the collecting was done, as con- 
trasted with the borders, was less affected with these invaders and more 
nearly agreed with the original forest biota. The general appearance 
of the habitat is shown in Fig. 4. The interior of the forest, showing the 
deciduous undergrowth and giving some idea of the stratification of the 
plant societies, is shown. 

The soil was examined by methods used in the examination of the 
Mount Ktaadn soils, which in turn were adaptations of the procedure 
of Adams (1920) in the examination of the Mount Marcy soils. Chemical 
and physical analyses were made, but the specific acidity was not taken. 
The sample was taken as follows: the pine needles and other forest floor 
trash were brushed away, and a hole was dug in the ground. A sample 
of the upper eight inches of soil was shaved off with a spade and placed 
in acan. The results of the analyses are given in tabular form (Table 
VII). It will be seen that this mainly a clay and silt soil, possessing much 
less sand than the least sandy of the mountain soils examined. Its nitrogen 
content is also higher than that of any of the soils examined for the moun- 
tain. Its acidity was much lower than any except the heath tundra. This 
soil was quite wet during the earlier part of the study, but in the latter 
part of the summer it became drier and friable, at least down to the depth 
(about 10 cm) which was examined for animal population. No doubt 
this was in part due to the rather scanty herbaceous cover over portions 
of the area examined. 

The temperature was recorded by means of thermographs, and self- 
registering thermometers, the latter being read at critical periods, as will 
be seen later for the individual instruments. The self-registering maximum 
and minimum instruments were all checked by a standard instrument, 
and were in turn used for setting the thermographs. Throughout the 


407) A COMPARISON OF ANIMAL COMMUNITIES—BLAKE 43 


period of study temperature records were taken for soil, shrub and tree 
strata, and for a considerable period during the latter part of the study 
records were taken for the dead leaf stratum as well. 

The instrument used for the measurement of soil temperature was 
a maximum and minimum thermometer, which had been corrected by 
comparison with a standard instrument. This was placed in the ground, 
just below the layer of dead pine needles and forest-floor debris. The 
exposure was made as follows: 1.5 m west of the lower instrument shelter 
(see below), in a plat shaded by young maples and balsam firs, a rec- 
tangular hole was dug, .4 m deep, .3 m long, and .2 m wide. This was 
lined, sides and bottom, with wire-screencloth on a frame, to keep out 
debris and to keep the sides from falling in. The whole was covered with 
a heavy grating of wooden bars, overlapping generously on all sides, 
which was laid on the ground to cover the opening. This grating was 
in turn covered with galvanized wire screen, on which was placed a mat 
of dead needles, organic trash from the forest floor, top soil and plants 
growing thereon, just as it was scraped up from the adjacent forest floor. 

The whole was designed to make a chamber, in which instruments 
could be exposed, surrounded by the soil and covered by the dead leaf 
layer. The thermometer was exposed in this, a small hole being cut in 
the wire screen between two of the slats of the grating, through which 
the instrument could be drawn up, read, set and returned. At other 
times this opening was kept covered with a piece of bark. 

Readings were taken twice daily, at 7 A M and at 7 P M with few 
breaks in this procedure. During the greater part of the study no attempt 
was made to take a set maximum (maximum reading immediately after 
setting), since this exposed the instrument so long to the air temperature 
that it tended to respond thereto, before it could be lowered into the ob- 
servation cavity. The instrument, was, therefore, quickly withdrawn, 
read, set, and as quickly returned, usually before the air temperature 
had time to affect the mercury, and always before it had time to affect 
the indicator (reading). The results of the readings appear in tabular 
form (Table VIII) and in graphic form (Figs. 10 and 11, curve labelled 
C). 

Temperatures of the leaf-stratum were not taken until July 19. At that 
time a soil thermometer was exposed by being thrust 8 centimeters into the 
leaf and debris layer of the forest floor, in a spot shaded with young firs and 
birches (none over .8 m in height) 2.5 m east of the lower instrument 
shelter. It was thought that this would give a more reliable temperature for 
the leaf layer on the ground, than the thermometer exposed in the soil 
observation chamber under this dead leaf layer. The instrument was read 
twice daily, at 7 A M and at 7 P M, and during the latter part of the study 
an additional reading was taken in the early afternoon whenever possible. 


44 ILLINOIS BIOLOGICAL MONOGRAPHS [408 


The data so obtained are tabulated (Table IX) and shown as curve D 
in the plate and figures referred to above. 

The air temperature at the level of the shrub stratum was taken by 
instruments exposed in an instrument-shelter of the standard Weather 
Bureau type, with louvred sides and slatted bottom, thus protecting 
the instruments from the direct effects of rainfall or sunshine, but per- 
mitting a free circulation of air around their sensitive elements. Through- 
out the study a United States Weather Bureau type maximum and mini- 
mum thermometer and a thermograph were left in this shelter, which 
was about .6 m above the ground on the north side of a large white pine. 
The thermograph placed here was frequently checked with the maximum 
and minimum thermometer, with which it was exposed. Its records 
were kept throvghout the summer, but as its recording principle was 
somewhat defective, and it showed a consistent lag of at least two degrees, 
which could not be overcome by anything that could be done in the way 
of lightening the drag of the lever and increasing the air exposure of the 
responding metal parts, the records taken with it have not been included 
in the present report. In their place have been substituted records taken 
with the maximum and minimum thermometer. 

This instrument, which from its accuracy was used in checking the 
others used in the study, was read as far as possible twice daily, at 7 A M 
and at 7 P M. During the latter part of the study another reading, in 
the early afternoon, was taken daily. The results appear in Table X 
and as curve A on the plate of temperature data cited above. 

A thermograph was exposed in an instrument shelter, of the same 
type of construction as the one just described, which was suspended 
11 m above the ground on the north side of a large pine, in a moderately 
thick growth of white and Norway pines (Fig. 4). While not at the top 
of the forest crown, this shelter was among the upper branches and far 
above the tops of the deciduous trees growing among the first growth 
conifers. The shelter was suspended by a rope and pulley from a protect- 
ing pent-house cover, and could be lowered to change the sheets and check 
the contained instruments, as was done every Monday and from time to 
time during the week. This thermograph was a very reliable instrument 
indeed, gave no mechanical difficulty and checked well, showing little 
or no lag, with the U. S. Weather Bureau type thermometer, when both 
were exposed to like conditions. From it was gained the data given in 
Table XI, and shown as curve B on Figures 10 and 11. 

The record sheets on recording instruments were changed Monday 
morning. The method used in the translation of the recorded curve to 
figures of maxima, minima and means was a modification of that suggested 
by Weese. He estimated the mean temperature for each two-hour period 
on the ruled charts, and used the average of these means as the weekly 


409] A COMPARISON OF ANIMAL COMMUNITIES—BLAKE 45 


mean temperature. It was found by computing charts in this way and 
by the method of averaging the actual temperatures recorded at the end 
of each two hour interval that the results were practically identical over 
the period of a week, and inasmuch as this latter was somewhat of a time 
saver the method was adopted. Dr. M.S. Johnson, who suggested this 
method and has employed it himself, states that in all cases the results 
gained from computing charts by these two methods show insignificant 
differences, and this irrespective of whether the weekly fluctuations 
are great or small and the curves in consequence abrupt or smooth. For 
shorter periods no doubt the actual two-hours means would have to be 
computed. A base mean was computed in accordance with that used by 
Weese, that is the average for the week of the mean temperatures exist- 
ing during the comparatively stable period of the day between 8 P M 
and 6 A M; this of course was not practicable for the simple instruments 
used, and was employed only in the case of the thermographs. Besides 
this the soil and leaf strata hardly show sufficiently marked fluctuations 
to make the attempt to determine a base or night mean of value, even 
had recording instruments been available. 

For all stations absolute maxima and minima, mean maxima and 
minima, mean temperatures and extreme and mean ranges for each week 
of the study were computed; for the upper tree station was figured in 
addition the weekly base or night means and the deviations (mean) above 
them. -The data is presented in Tables VIII, IX, X and XI, and in Figs. 
10 and 11. 

Since it has been seen that the soil temperatures show a marked 
lag behind the air temperatures, in their response to the general mete- 
orological conditions, it will be best to take them up last. The air tem- 
peratures show two high points during the study, occurring during the 
weeks of July 14 and August 11, and were showing another marked up- 
ward tendency at the time the study was closed. The lower, earlier por- 
tions of the curves indicate the general rise of the spring temperatures 
up to the time of the July maximum; this is of course broken by minor 
fluctuations. The study was closed too early to show any traces of the 
autumnal fall. The actual fluctuations of the temperature as observed 
are probably not of any great significance; they do, however, show a 
considerable range of variability in the air temperatures of this habitat 
as a whole. If we consider now the stratal differences in temperature, 
we see that, while for a rather considerable period the temperature in 
the upper tree stratum is above that of the layer of air near the ground, 
especially during the middle and latter part of the study, still this is by 
no means always the case, nor as consistently the case as Weese found 
for similarly placed instruments in Illinois elm-maple forest. This may be 
explained by the position of the upper instrument which, while high 


46 ILLINOIS BIOLOGICAL MONOGRAPHS [410 


enough to be independent of ground and undergrowth influences, was not, 
because of the great height of the trees and the fact that their branches 
were thickest at the top, in the forest crown but below it, and hence covered 
by a heavy canopy of branches from the direct effects of the sun. 

Of more interest in the present problem are the temperature rela- 
tions of the layer of air just over the surface of the ground and those 
of the ground itself and the stratum of dead leaves that covers it. It 
is an axiom that soil temperatures in general and forest soil temperatures 
in particular, are more stable than the overlying atmospheric tempera- 
tures, and the causes are obvious (Adams, 1915). One of the factors 
in this phenomenon, the equalizing effect of the layer of forest-floor debris, 
is of interest in connection with the study made of temperatures found 
in this latter stratum. It will be seen that the temperature of this latter 
closely accompanies the soil temperature, but is, on the whole, more re- 
sponsive to the general atmospheric temperature conditions, as might 
be expected, rising before the soil temperature in periods of rising tempera- 
tures and falling first during periods of falling temperatures. In general, 
our figures indicate a stratification of temperatures, with the steepest 
gradient between the leaf and shrub levels, whereas the two upper and 
the lower strata examined show temperatures accompanying each other 
more closely. All, however, show a fairly uniform agreement, maxima 
and minima developing together in the different strata with unimportant 
exceptions, and the temperature showing a general rise from the lowest 
to the highest strata. 

If we now consider the temperature ranges in the different strata, 
we see a more complete stratification than is shown for weekly mean tem- 
peratures alone. The forest upper strata show a high degree of variation 
for a single week, and thence the index of variation decreases downward 
until we reach the soil, where the variations are smallest and the temper- 
ture relatively uniform. There is a well-marked difference in the extent 
of temperature variation between the tree and shrub strata, and some, 
but less conclusive evidence of stratification between the leaf and soil 
strata. But the great break, as in the actual mean temperature curves, 
lies between the leaf and shrub conditions. Here, as in deciduous forest 
“in summer the temperature increases from the soil upward to the forest 
Crown; 6. 2 as the temperature is most variable in the forest crown 
and least so in the soil’’ (Weese). 

Humidity of the atmosphere was measured at the herb-shrub level 
and 11 m above the ground. The instrument used to measure the re- 
lative humidity of the lower strata was a hair-hygrometer which, after 
adjustment by a standard instrument, was exposed in the lower instru- 
ment shelter with the thermograph and maximum and minimum ther- 
mometer used for measuring the temperature of the lower air strata; 


411] A COMPARISON OF ANIMAL COMMUNITIES—BLAKE 47 


this shelter was in turn partly shaded by young maple and balsam fir. 
This hygrometer was used as the standard instrument, by which the 
hygrograph in the upper (11 m above ground) instrument shelter was set 
and checked. It was read twice daily, with a few exceptions, at 7 A.M. and 
at 7 p.m. During the latter part of the summer an additional reading 
was taken on most days early in the afternoon. 

The only hygrograph (recording hair hygrometer) available for the 
study was exposed in the upper instrument shelter along with the ther- 
mograph used for recording temperature at that level (11 m above the 
ground, Fig. 4). It was a sensitive instrument, and checked well with 
the hair hygrometer used to set it, when both were exposed to the same 
conditions. 

The tables (Table XII and XIII) and Figures 12 and 13 give the 
data obtained from these instruments, which was computed in a manner 
similar to that used for the computation of temperatures. Here, however, 
the base mean (Weese) is high instead of low, as the humidity almost 
always reached 100% sometime between the hours of 8 P M and 6 A M. 
Absolute maxima and minima, mean maxima and minima, mean relative 
humidity and total and mean ranges are tabulated for both stations; 
in addition the base mean for each week and the mean range below it 
are given for the upper station, where alone a recording instrument was 
available. 

The curve of relative humidity of the herb-shrub stratum shows 
several high and low points which are not correlated with temperature 
differences, as far as can be seen. Neither are the extreme differences 
shown (18% of relative humidity) sufficient to be of any marked signif- 
icance, since the fluctuations of a single day may reach a figure of 69% 
at the same station. The curve of mean relative humidity for the tree stra- 
tum is consistently lower, with a single exception, than that at herb-shrub 
level. This is the usual condition, because at the lower station the moisture- 
laden atmosphere in contact with the more or less damp forest-floor, 
is less rapidly removed by air currents and its place taken by the drier 
air coming from over adjacent cleared land. The average difference be- 
tween these two stations for the period studied was 7.5% relative humid- 
ity, as compared with the figure 3.5% given by Weese for deciduous 
forest. The discrepancy is no doubt due to the fact that the present 
study was made entirely in the summer, when such differences are at 
their greatest. While the study of deciduous forest conditions by Weese 
embraced a complete annual cycle, his humidity data for the tree stratum 
were not taken during the early part of the summer. 

The curves of mean ranges for the two stations (Fig. 13), show a con- 
dition of large variation, both relative and actual. Particularly is this 
true of the tree stratum. This agrees perfectly with the finding given 


48 ILLINOIS BIOLOGICAL MONOGRAPHS [412 


for deciduous forest that between the herb and shrub strata on the one 
hand and the tree stratum on the other there is ‘almost invariably greater 
mean relative humidity in the former situation and a greater mean daily 
range in the latter” (Weese). The most casual glance at the curves shows 
that this might have been as well said for the conditions of relative humi- 
dity stratification found by the writer. The mean daily range curves 
are entirely distinct throughout. 

It will be seen that the upper strata of the forest air are regions of 
lower relative humidity and more marked fluctuations in this factor 
whereas the lower strata, adjacent to the ground, are regions of some- 
what higher relative humidity and immensely greater stability. The 
significance of these factors and their effect on the animals will be discussed 
in due course. 

Since the evaporating power of air has generally come to be considered 
as the most reliable general index of all the other physical factors which 
affect organisms of terrestrial habitats, an attempt was made to measure 
this factor in the coniferous forest area studied, especially in its relation 
of stratification. The instruments used were Livingston porous-cup atmom- 
eters of the spherical type, which were exposed at nine stations at various 
localities and strata of the forest habitat. Of these, the records of one 
instrument, a black atmometer exposed with a white one for measure- 
ment of light effects, have not been included, since there was no other 
similar instrument with which to compare it. 

The instruments employed were new and standardized cups direct 
from the makers. They were restandardized at the close of the study, 
but were not standardized during the study, of which the actual dura- 
tion was about nine weeks. For comparison with each other, the read- 
ings taken each week were changed by a coefficient to those of a standard 
instrument. 

For field use the atmometer cups were mounted on quart bottles 
by the simplified non-absorbing mounting described by Livingston and 
Thone (1920). The weekly filling was done Monday, by means of a burette, 
the bottles being filled to a file-mark on the neck of the reservoir bottle. 
As indicated by the results, the quart bottles were larger than needed 
for weekly studies in this climate and habitat; for field-work in north- 
eastern (or probably northern) coniferous forest, a pint bottle would 
be sufficiently large, and would practically halve the amount of distilled 
water that must be carried. 

The exposure of atmometers was as follows: 

No. 1, Black spherical atmometer exposed one meter above ground, 
and 2 meters from the lower instrument shelter, under the leafy branches 
of a young maple. 

No. 2, White spherical atmometer exposed 1 meter above ground 
with No. 1. 


413] A COMPARISON OF ANIMAL COMMUNITIES—BLAKE 49 


No. 3, White spherical atmometer exposed near surface of ground 
(0.3 meter above surface) near Nos. 1 and 2 and, save for height, under 
identical conditions. 

No. 4, White spherical atmometer 2.5 meters above ground, in cy- 
lindrical basket of galvanized wire hanging from lower limb of small 
hemlock 4 meters northeast of the lower instrument shelter. 

No. 5, White spherical atmometer exposed with the maximum and 
minimum thermometer in the observation chamber in the soil already 
described; the sphere was just beneath the grating, covered with the 
usual layer of pine needles and other forest-floor debris. 

No. 6, White spherical atmometer exposed for two weeks at the be- 
ginning of the study on the ground among high grasses in a swampy 
glade on the eastern edge of the forest. There was no forest cover, in 
the ordinary sense of the word, although the glade was surrounded by 
a dense growth of high bushes, so that there was little wind, although 
the sun shone there brightly during most of the day. 

No. 7, White spherical atmometer exposed 6.5 meters above the 
ground in cylindrical basket of galvanized wire suspended from the upper 
instrument shelter on north side of large pine tree (Fig. 4, about the middle 
of the picture). 

No. 8, White spherical atmometer exposed 11 meters above the ground, 
in bracket attached to side of upper instrument shelter (Fig. 4). 

No. 9, White spherical atmometer (same instrument as No. 6) exposed 
from July 7 in a position among grass and herbage on the western edge 
of the forest, where the latter meets a wide area of grassland. Here it 
remained until August 4, when it was destroyed by children. 

The results of the entire series of observations are given in tabular 
form (Table XIV) and shown graphically. Figure 14, shows the curves 
of evaporation by stations, through the period of the study and Figure 15 
the mean amount of weekly evaporation from each instrument for the entire 
period. 

The curve of evaporation from the atmometers directly exposed to 
the air showed a general increase for the first three weeks of observation, 
thus reaching a high level which it maintained, with slight up and down 
fluctuations, for the next month. At the end of that period, evaporation 
in all forest stations decreased sharply, the most marked change taking 
place in the upper stations and thence decreasing gradually towards 
the ground stratum. Following two weeks of this decrease, the second 
week more gradual, the trend of evaporation again turned upward, and 
rather sharply, for the final week of observation. The earlier changes appear 
to be some degree independent of the amount of rainfall during the weeks 
when they occurred; thus the evaporation of the first three weeks mounted 
steadily, in the face of a decreasing precipitation, perhaps assisted by 


50 ILLINOIS BIOLOGICAL MONOGRAPHS [414 


the moderate rise of temperature during the same period. Also the high 
rate of evaporation maintained during the next four weeks accompanied 
a generally decreasing rainfall, the highest point reached on the week 
of August 4 following a period of two weeks when the precipitation was 
very light indeed. Following this, however, the evaporation fell off rapidly, 
as has been seen, and did not rise again until considerable precipitation 
had occurred. From these things we might infer that the conditions of 
coniferous forest are such as to cause a moisture retention, a reservoir, 
as it were, of the abundant precipitation of the winter and spring months; 
from this supply of moisture, evaporation increases, in part due to increas- 
ing summer temperatures, until the latter part of the summer, when evap- 
oration falls off unless the moisture of the forest habitat is restored by 
further precipitation. In this connection it may be said that the con- 
dition of the soil and pine needles layer of the forest lower strata, as ob- 
served for moisture during the period of the study, exactly bore out this 
conception. 

Of the various physical factors thus far considered, the evaporating 
power of the air shows the most complete evidence of stratification (Figs. 
14, 15). It will be seen that none of the station evaporation curves over- 
lap at any portion of their extent. It appears that the evaporating power 
of the air, as found in this habitat, shows two large breaks with steep 
gradients in stratification, one between the ground and leaf strata on the 
one hand and the herb stratum on the other; and one between upper shrub 
or high bush stratum and the tree station, low and high, proper. This 
will be most apparent if Figure 15 is examined without regard to columns 
6 and 9, which represent evaporation at stations outside the forest proper, 
but it is also indicated in Figure 14. In other words, going from the floor 
of the forest upwards, we have first, under the leaf layer on the forest 
floor, a condition of very low evaporation; thence we pass, by the steep- 
est gradient in the series, to the group of stations represented by Nos. 
3, 2 and 4, which form a group of herb, shrub and high bush strata, be- 
tween which the gradients are of the same order; above this is another 
steep gradient, separating stations No. 4 and No. 7; both these last con- 
stitute a group of tree strata proper, and between the two the gradient 
is again “easy.” The cause of the first and sharpest cleavage will be 
evident at a glance; the cause of the second is suggested by looking at 
Fig. 4. It represents the crowns of the lower-growing deciduous under- 
wood of the much higher coniferous forest. 

If we take as a standard atmometer No. 2, 1 m above the surface 
of the ground, we see that there is a constantly lower evaporation here 
than in the tree 1.5 m above, and that the differences between the two 
levels are moderate in amount, and both actually and relatively higher 
with periods of high evaporation. The relative evaporation from these 


415] A COMPARISON OF ANIMAL COMMUNITIES—BLAKE $1 


two levels does not show the relations with precipitation for the period 
found by Weese for corresponding stations in elm-maple forest; so far 
so far as can be seen, the points of greatest difference between the eva- 
poration at the two levels fall on weeks showing widely varying degrees 
of precipitation. 

The evaporation from instrument No. 7, 6.5 m above the ground 
shows, as we have seen, a sharp and constant differnece from that of 
No. 4 just discussed. This instrument was well above the tops of the 
deciduous underwood, and therefore might be expected to show evapora- 
tion of a different order of magnitude from that shown by all the instru- 
ments below their level. Not only is this found to be true, but its curve 
never even approaches that of the next lower stratum (No. 4) except at the 
time of lowest evaporation, and then not closely. 

The maximum evaporation was that for instrument No. 8, exposed 
11 m above ground. This followed throughout, however, the type of 
curve followed by the other instruments exposed directly to the air. 
It is of the same order of magnitude, as faras its weekly means of evap- 
oration are concerned, as the 6.5 m instrument just below it (No. 7). 
The reason for this has already been discussed. It should be remembered 
in this connection, however, that the 11 m instrument was by no means 
at the forest top; an instrument placed there would have added at least 
a minor and perhaps a major evaporation stratum to those already dis- 
cussed. 

Turning now to the instruments which were exposed below the 1 m 
level, we see that atmometer No. 3, 0.3 m above the ground, showed 
a constant and definite curve lower than that of the 1 m instrument 
(No. 2), and following it within expected ranges throughout the study; 
this instrument shows one break in the record, occurring for the week 
of August 4. While this curve is constantly lower than the curve of the 
instrument next above it, it will be seen that the differences are moderate 
in amount, and that the evaporation differences are of the same order. 
The constancy of the differences, however, is of interest. 

The most extreme results in the direction of small evaporation were 
obtained in the case of the instrument which was exposed in the observa- 
tion chamber under the artificial mat of pine needles and debris. This 
instrument may be supposed to have given some idea of the amount of 
evaporation occurring from the top soil through the dead leaf stratum. It 
will be seen that the value is very low throughout the study, never exceed- 
ing a single cc and sometines falling to almost nothing, although a measure- 
able evaporation was always present. Still more interesting is the extent 
to which the extremely low curve agreed, in its weekly fluctuations, with 
the curves of the instruments exposed directly to the air in the strata 
above ground. It is interesting that the atmometer should be found 


52 ILLINOIS BIOLOGICAL MONOGRAPHS [416 


sufficiently sensitive to respond to differences communicated to it through 
a three-inch layer of forest-floor debris. The average weekly difference 
between the evaporation here and in the first (0.3 m) level above the 
ground is practically 8 cc for the habitat studied, the greatest found 
between the evaporating powers of any two adjacent strata. 

The curves for evaporation at the forest-edge stations have not been 
given. The weekly mean of evaporation for the period over which they 
were studied is illustrated graphically in Fig. 15 where the columns rep- 
resenting these two stations are placed in the general series of forest 
stations, in the order to which their magnitude entitles them. If we examine 
column 6, the record for a swampy open glade outside the forest on the 
east, we see that it possesses the lowest evaporation value of that found 
for any station except the sub-leaf one. Here, in an open but swampy 
glafle, surrounded by high grass, and cut off by surrounding bushes and by 
surrounded by high grass, and cut off by surrounding bushes and by 
the forest itself from wind, and especially from the prevailing fair and 
drying westerlies, evaporation is even lower than anywhere above ground 
in the forest. 

On the other hand, column 9, representing the mean weekly evapora- 
tion for an instrument exposed among grass and herbage on the western 
forest margin, and just at the edge of wide tracts of grassland, showed 
an evaporation higher than that observed anywhere in the forest below 
the upper strata. The influence of wind is no doubt preeminent here. 
The differences between these two forest margin stations indicate that 
conditions at this tension zone may be very different under different local 
conditions—more so, in fact, than stratal differences within the forest 
itself. 

Considering further Fig. 15 it will be seen that the actual order of 
increase in evaporation, beginning at the lowest, as seen in the entire 
series of observations is: sub-leaf stratum, swampy forest-margin, herb 
stratum, shrub stratum, high bush stratum, dry forest margin, low tree 
stratum, high tree stratum. The actual figures of mean daily evaporation, 
as expressed in this order, are: 


Station 5 *6 3 2, 4 *9 il 8 
Height 
inm. -.08 0.3 0.3 1.0 2.5 0.3 6.5 11.0 
Mean wk. 
evap. co. 0.2 6.2 8.2 11.2 14.0 17.4 19.7 21.0 


Speaking of deciduous forest, Weese (1924) says: ‘The gradient 
in the evaporating power of air in the forest is very striking,—stations, 
less than a meter apart, vertically, showing definite and constant differ- 


*Forest margins. 


417] A COMPARISON OF ANIMAL COMMUNITIES—BLAKE 53 


ences. This is particularly true at the lower levels. At the higher levels 
the gradient still persists but is subject to irregularities due to the greater 
exposure and lack of uniform conditions.’’ All this equally true for conif- 
erous forest, and even more regular and constant. The absence of seasonal 
changes in vegetation of the upper strata would tend to obviate some of 
the interlocking of the upper strata curves found by him as coming about 
the time of the leaf-fall. ‘The relative seasonal differences of the evapora- 
ting power of air in coniferous forest might be as marked for spring, fall 
and summer, as those found by him in deciduous forest, especially in 
forests where there is an abundant herb, shrub and low tree strata of 
deciduous plants. 

Here, rather than at the forest crown of coniferous forests, should 
we expect to find at critical seasons the stratal irregularities in evapora- 
tion most marked; probably even here conditions would always be stable 
as compared with those in deciduous forest, where the entire forest cover 
is shed in the fall, since the cover of the conifers would have a stabiliz- 
ing effect. This has not been studied. 

The only apparatus available for measuring the light in the present 
study was a Wynne exposure meter, the ordinary photographic appara- 
tus of the sensitized-paper type; this was employed to get some idea 
of the relative light intensity under different conditions in the forest 
environment. This of course measures the actinic rays only (Shelford, 
1912); it has been pronounced fairly satisfactory for that purpose (Bates 
and Zon, 1922), and was the only type of illuminometer available. Regular 
readings were not begun until the early part of August, and some of the 
first ones taken showed so wide a range of variation, under what appeared 
to be very similar conditions of light, cover, etc., that they were discarded. 
However, it finally seemed best to take what readings were possible, 
in the hope that by averaging a number of these, some idea of the relative 
light intensity at the different stratal levels might be obtained. 

The readings were mostly taken in the early afternoon, and within 
as short a time as possible of one another; perhaps the average interval 
between readings may have been three minutes. The same sensitized 
sheet was used for all readings taken on a given day, to obviate any in- 
accuracy arising from the comparative freshness of the paper or the reverse. 
The darker of the two standard tints was the one used in matching, because, 
while this took longer to match in the darker localities, it was the only 
one which could be used with any accuracy in the stronger light, where 
the lighter tint was so soon matched that it was impossible to obtain 
even approximate accuracy. A stop-watch was used, and the readings 
as given are in seconds. 

A record was made of the general weather conditions at the time 
of each reading, as far as they could be described by the observer. In 


54 ILLINOIS BIOLOGICAL MONOGRAPHS [418 


the longer readings the amount of light changed perceptibly during the 
time taken to match the colors; this is indicated on the records under 
remarks on weather conditions. 

The readings were taken from the same stations throughout the study, 
which may be described as follows: 

On the Ground: The place was five meters east of the lower instrument 
shelter, in a spot covered with the typical amount of shade from young 
saplings (beaked hazel, ash and alder) and, of course the conifers. The forest 
crown begins about 5 m from the ground in this place, and becomes 
thicker higher up, but always is of a rather open character. The data 
from this station are given in Table XV. 

Above the Ground, 1.5 m. The actual locality was the same as for 
the ground reading, save for the elevation. The instrument was shaded 
by a growth of young maple. The data are given in Table XVI. 

In Open Glade: 25 m north of the tree bearing the upper instrument 
shelter. This place was covered by a forest-crown shade almost, if not 
quite, as dense as that for the two previous stations, but was characterized 
by the almost total absence, over an area about 30 m square, of the growth 
of shrubs and young deciduous trees, especially maples, which was char- 
acteristic of them. (Fig. 4, right foreground). The data are presented 
in Table XVII. 

In Open Grassland: 20 m from the western edge of the forest. This 
reading was taken in an attempt to get some idea of light intensity in 
the absence of forest cover, and hence the illumination of the forest crown, 
where it was impossible, for obvious reasons, to take actual measurements. 
The data taken at this station are shown in Table XVIII. 

Considering this data, it appears that there is a very definite strati- 
fication of light in the coniferous forest habitat and that the light avail- 
able in the lowest strata in a very small fraction of what is available higher 
up. In fact the imperfections of the method, especially of measuring 
the strongest light, probably make this fraction appear much larger than 
it actually is. It is interesting that the steepest light gradient should 
exist between the ground and the next stratum measured above it, a 
condition of things comparable to the position found for the steepest 
gradients of temperature, humidity and evaporating power of air. The 
relation between the light intensities in the glade and in the open tend 
in a general way to support the statement of Weese for deciduous forest, 
that the light which enters into large openings in the forest is little lessened 
in its intensity. Considering the reading made in the shaded but rather 
open glade, it is evident that the light there is a considerable fraction of 
that found in the grassland outside, whereas the light on the shaded forest 
or even above it under the shade of shrubs and small trees, is a very small 
fraction. The method employed was too rough to make these actual 


419] A COMPARISON OF ANIMAL COMMUNITIES—BLAKE 55 


figures of significance, either by themselves or for comparison with 
those taken with more elaborate instruments in other habitats, but 
the data indicate the fact, direction and to some degree the extent, 
of light stratification in the forest environment. 


THE BIOTA 


In studying the animals of the coniferous forest tract, and especially 
their stratification into societies, the methods of Weese (1924) were largely 
employed. The collections were taken most frequently during the latter 
part of the study; therefore the biotic data for the month of August is 
the most complete. Collections were made according to the quasi-quanti- 
tative method of sampling from the various strata, in the immediate vicin- 
ity of the stations where the instruments were exposed. Four strata 
were studied systematically, the soil, dead-leaf, herb and shrub; the 
tree stratum being neglected in the present study. On each date when 
collecting was done, these four strata were “sampled.” The dates given 
are those on the last day of the week when the samples were taken, thus 
corresponding with the instrumental observations, which are dated on 
the day they closed. In a few instances during the latter part of the season 
additional collections were taken in the middle of the week. The animals 
from the different strata were collected as follows: Weese’s original 
paper should be consulted for further details, as the writer closely followed 
his practice, in order that the data from the two habitats might be to some 
extent comparable. 

Soil collections were taken from the upper 10 cm of soil, from which 
the leaf cover had been previously removed. The soil was explored over 
an area 2 ft square, being carefully dug over with a trowel to the depth 
of 10 cm. Whatever animals were found in this plot were placed in vials. 

Leaf collections were made from the layer of dead leaves (largely 
pine needles) and other organic matter which covers the soil. This layer 
was swept up from the previously measured 2 ft quadrat, placed quickly 
in a cage-box made of very fine mesh wire-screening, and carried to the 
laboratory, where it was treated with ether and examined for its animal 
population. 

Herb collections were made by ten sweeps of an insect-net with a 
30 cm mouth over and among the plants of this stratum. 

Shrub collections were taken in the same way at the higher level; 
paper bags were used for carrying the last two samples to the laboratory. 

The quantitative results of these collections appear in Table XIX 
and in the form of a graph (Fig. 16). The latter gives by curves the total 
and stratal populations. 

The curve of total population (A) is seen to be a very irregular one. 
Starting with a medium position for July 7 it falls steadily through July 14 


56 ILLINOIS BIOLOGICAL MONOGRAPHS [420 


to July 21, and then takes a sharp upward trend for the week following. 
By August 11, when the next collection was taken, the population had 
again fallen, and it continued to fall, reaching by the middle of the follow- 
ing week the lowest point observed during the study. By the end of the 
week it had again mounted abruptly, but suffered another fall during the 
middle of the week of August 25. But by the end of that week it had 
mounted to the highest point reached at all, whence it declined somewhat 
to the last collection which was still, however, above the average. The 
peaks of this curve all fall in periods of relatively low temperature, but 
this is probably not significant, although Sanders and Shelford (1922) 
found high temperatures accompanied increased animal population in 
a.pine-dune animal associes, while Weese finds high temperatures in elm- 
maple forest conducive to low animal populations. It is unlikely that 
the animals of cool, moist coniferous forest would be restricted in numbers 
by temperatures no lower than the lowest of those recorded. Entirely 
similar types, inhabiting the still cooler alpine spruce-fir forests of Mount 
Ktaadn appear to be independent of much greater temperature extremes 
than this, in all matters save that of a daily rhythm of activity. The 
marked high points on the curve appear to be largely due to the presence 
of certain particular species whose numbers attained a maximum, rather 
than to any general increase in the numbers of any considerable num- 
ber of the species making up the population. Thus one of the highest 
points is produced by the large numbers ‘of Chrionomidae taken on 
July 28. 

If we consider now the size of the various stratal populations, we see 
at once that the shrub stratum contains the largest and also the most 
fluctuating animal population. This condition is the reverse of what has 
been described for deciduous forest by Weese, where the population of the 
herb stratum is uniformly larger than that of the shrub stratum. An 
examination of the curves given in Fig. 16 shows that for the area and 
season studied the numbers of shrub animals were rarely below, and often 
much above, the numbers of herb animals. The shrub stratum in fact 
to a large degree controlled the general population curve, especially in 
its extremes. This is probably in part due to the scanty herb cover in 
the coniferous forest habitat. The first of the two marked maxima shown 
by the shrub curve was, as has been said, caused by Chironomids; the 
second, that of August 25, was due to several species of Hemiptera and 
Homoptera. 

The herb stratum was second in size and rather uniform, though pre- 
senting some fluctuations in numbers during the latter part of the season, 
These maxima were caused by several species of insects and young spiders, 
which will be taken up in more detail under the study of individual species 
in their relation to the stratal societies. 


421] A COMPARISON OF ANIMAL COMMUNITIES—BLAKE 57 


The population of the dead-leaf ground stratum was considerably 
lower, on the average, than that of the herb stratum, and might have 
been expected to have been lower still in comparison. No doubt this 
was influenced by the relatively low numerical value of the herb stratum 
in this habitat, as compared with the same society in deciduous forest. 
The soil stratum was of low value throughout, but very uniform. Its 
population is largely a resident one, as far as the dominant animals are 
concerned, 

The entire animal population as collected is given numerically in 
Table XIX. 

With a few exceptions only the predominant animals of the various 
strata will be discussed, present in such numbers, as compared to the other 
species, as to play an important part in the community. Certain animals 
were very scarce or wanting; only a single mollusk was taken during the 
entire season, Phylomycus carolinensis (Bosc), on August 22; the coniferous 
forest habitat is poor in this group (Walker, 1906). 

The birds of the area were not studied. An attempt was made to 
get at the size and composition of the mammalian population by ex- 
tensive trapping during the latter part of the season. The results of 
this were somewhat surprising. Only two species of mammals were trapped 
and one of these, the shrew Sorex personatus, was rare. The other, the 
short-tailed shrew Blarina brevicauda talpoides, was very abundant, In 
all the trapping done not a single specimen of the white-footed mouse, 
jumping-mouse or short-tailed meadow mouse was taken, although the 
first might have been confidently expected throughout the habitat, and 
the last in the grassy regions abutting on the swampy eastern area. It 
was not possible, because of lack of time, to investigate other territory 
in order to find out whether the scarcity of usually common animals was 
general in the vicinity. The area studied was not far from the college 
poultry-plant, and there were outlying chicken-pens within a few hundred 
yards. For this reason, there was always a number of smaller carnivores 
hanging around this forest tract, especially skunks and half-wild cats 
It is possible that this fact may have had something to do with the absence 
of mice through the area studied; whether or not carnivorous animals 
show any preference to mice, as contrasted with the pugnacious and 
rank-fleshed shrews, is not known. The latter are certainly sometimes 
eaten. The red squirrel was the only other mammal noted. 

If the general population curve (Fig. 16) is inspected, and still more 
if the curves representing the seasonal abundance of dominant species 
are examined (Figs. 17-20), it will be seen that the greater part of the study 
fell between the period of the high vernal rise in population and the later 
aestival rise, including only a little of the last part of the former but 
largely covering the latter. Further, if we omit from consideration forms 


58 ILLINOIS BIOLOGICAL MONOGRAPHS [422 


not strictly belonging to the forest habitat as such but incidental on the pres- 
ence of nearby aquatic habitats, especially the chironomids, we see that 
this relation becomes even more apparent. The study did not last sufficient- 
ly long to show the entire march of the summer societies, but it indicates 
some of the phases of the series. Since the only well-developed seasonal 
society occurring in the study was the aestival, the dominants of that 
alone will be discussed in detail. These fall into well-defined stratal 
societies. Listed in order of abundance they are: 


CLASTOPTERA (SHRUB) SOCIETY 
Subinfluents: Clastoptera obtusa (Say), Tetragnatha sp. (juvenile), 
Graphocephala coccinea (Forst.), Macrosiphum coryli Davis, Philodromus 
sp., Diaphnidia pellucida Uhl. 


LEIOBUNUM (HERB) SOCIETY 


Predominants: Chironomus dispar Meig., Chironomus modestus Say, 
Leiobunum politum Weed, Chironomus decorus Johann., Tanypus melanops 
Meig. 

Subinfluents: Dicyphus famelicus (Uhl.), Nabis sp. (juvenile). 


Tomocerus (LEAF) SOCIETY 


Subinfluents: Tomocerus flavescens Tullberg var. separatus Folsom, 
Linyphia sp. (juvenile). 


HELopRILUuS (SOIL) SocIETY 

Subinfluent: Helodrilus caliginosus trapezoides (Dugés). 

It will be seen that the predominants are mostly arthropods. Mollusks 
were, as has been seen, almost wanting. Among the insects, only a few 
species of Lepidoptera and Hymenoptera had been been determined 
when the study was completed; these orders may have contained pre- 
dominant species. The same is true for certain dipterous larvae and for 
various myriapods, some of which were quite numerous in the lowest strata. 
It is interesting to note that no Coleoptera appeared among the dominants, 
and that this order was in general poorly represented; this a group which 
Weese found to be decidedly predominant in elm-maple forest. Here 
their place seemed taken by ecologically equivalent phytophagous Hemip- 
tera. 

Figs. 17-20 give the observed seasonal and stratal (for some species) 
distribution of the more important predominants. The curves of dis- 
tribution through the season are in some instances separated to show the 
stratal occurrence of the species in different stratal societies, such curves 
being separated and placed one over the other. The time is the same 
for all the figures and agrees with the scheme used for the presentation 


423] A COMPARISON OF ANIMAL COMMUNITIES—BLAKE 59 


of temperature and humidity data (Figs. 10-13). The increments used 
in plotting the heights of the curves may be different for different species, 
and the polygons have been smoothed. 


Clastoptera (Shrub) Society 

Clastoptera obtusa (Say) Fig. 19, Aa and b. 

According to Osborn (1916) the alder spittle-insect, under Maine 
conditions, hatches in late spring or early summer (July) and is common 
in the adult condition until early August, appearing afterwards, how- 
ever, until September. It did not appear in the collections until August, 
when it suddenly appeared and thence its total population mounted 
until the close of the study. Its stratal distribution showed a marked 
downward movement for the middle of the weeks of August 18 and August 
25, the numbers of animals decreasing in the shrub and increasing in the 
herbstrata. It will be noted that this is accompanied by a period of falling 
temperatures. This was also a period of falling evaporation. With rising 
temperatures and rising evaporation the herb population fell to nil, and 
the largest number of this species recorded for the study appeared in 
the shrub stratum about the first of September. This insect is said by 
Osborn to pass the winter in the egg stage; whether or not the sudden 
appearance of the adults in numbers so late in the season was an inward 
forest migration, similar to that observed by Weese for many beetles, 
cannot be definitely stated. The facts suggest it, but since this animal 
does not hibernate in the adult stage they are less conclusive in this 
instance. 

Tetragnatha sp. (juvenile) Fig. 18, c. 

These spiders were all young, which were abundant in the shrub 
stratum, during the latter part of the summer, preying on the smaller 
insects. They were not taken until the later part of the study and thence 
were present in slightly varying numbers throughout the remainder of 
the season, being sometimes taken in the herb stratum. Their maximum 
as adults comes earlier in the summer, before the greater part of the collect- 
ing was done, and they winter as young in the forest floor (Emerton). 

Graphocephala coccinea (Forst.) Fig. 19, Ba and b. 

This widely distributed leaf-hopper occurred in collections taken 
throughout the study. From the records of its occurrence in Maine, 
summarized by Osborn (1915), it appears to be generally characteristic 
of the late summer animal society, no records being cited earlier than 
August. It is characteristic of the moist forest habitat and occurs generally 
there on the herbs (especially ferns) and shrubs, etc.; it has been taken 
from the spruce-fir forest of Mount Ktaadn, no doubt from deciduous 
herbs and underwood. In the present study the animal was distinctly 
more a shrub species, although a constant smaller herb population existed 


60 ILLINOIS BIOLOGICAL MONOGRAPHS [424 


until the end of the collections, when the species disappeared from this 
stratum. There was a gradual increase in the total numbers, the species 
maximum being reached about the middle of August. As in the case of 
the alder spittle insect (Clastoptera obtusa Say) there appeared to be a 
response to the falling temperatures about August 18, the numbers of 
individuals falling off in the shrub and increasing in the herb strata, 
thus indicating a downward movement of the animals with the descend- 
ing temperature. 

Macrosiphum coryli Davis. Fig. 20, A. 

This aphid is one of the few dominants which show the peak of abun- 
dance as occurring in the early part of the period of study. From thence 
it fell off gradually, but was present in varying but smaller numbers 
throughout the remainder of the time. It was principally a shrub-society 
animal, but sometimes occurred at the herb level, and a single specimen 
was taken from the leaf layer—no doubt fortuitously. Adults and young 
were taken on various dates during the entire period when collecting 
was done. 

Philodromus sp. (juvenile). 

The young of this crab-spider (probably representing several species) 
were found at the same levels frequented by the adults earlier in the season, 
in low shrubs within two or three feet of the ground. They were occasion- 
ally taken from the herb stratum lower down, where they did not occur as 
predominants. Like the other young spiders they reached their maxiumum 
of abundance during the month of August. 

Diaphnidia pellucida Uhl. Fig. 20, D. 

This mirid, like most of the other dominant insects, had an aestival 
maximum, occurring in the early part of August, at which time it appeared 
suddenly in the collections. Thence it decreased rapidly in numbers, 
none being taken after August 25. It was sometimes taken from the 
lower (herb) strata, but was principally a shrub animal. 


Leiobunum (Herb) Society) 

Chironomus dispar Meig. 

This species was the predominant animal in numbers, but a species 
locally present, due to the damp habitat and aquatic and semiaquatic 
conditions found on the eastern border of the area studied. From the 
numbers, however, and the fact that it is often found in such coniferous 
forest stations, it seemed best to consider it among the list of predominants, 
with the above explanation. Considering the population as a whole, the 
peak of the midges appeared in the first collections, and after that there 
was a marked fall in numbers, followed by a second rise the latter part 
of the month of July; from this the curve fell again abruptly, to rise some- 
what in the early part of August, but not attaining another high point 


425] A COMPARISON OF ANIMAL COMMUNITIES—BLAKE 61 


during the period of the study. This group, then, did not take part in 
the late August population increase, but shows, like Macrosiphum, the 
last of a vernal maximum, and an additional mid-summer maximum be- 
sides. It is largely to this fact that we get the high point on July 28 in 
the general population curve, the contributing factor being a large number 
of Chironomids of several species taken on that date. 

If now the particular species Chironomus dispar Meig. is considered, 
it appears that this species, while taking part in the vernal maximum of 
July 7, did not attain its second maximum until August 4, or a week after 
the general high point for the family. Between these two dates lies a period 
of lower numbers, caused by the sudden decrease from the July 7 maximum 
and the gradual increase to the early August maximum; after the last 
date the population of this species again falls, but some individuals were 
present up to the end of the period of study. The decrease, sharp in both 
cases, does not appear to be connected with temperature or evaporation. 

Chironomus modestus Say 

This midge, as far as our collections indicate, did not take part in 
the general maximum of population observed for the family on July 7, 
but its midsummer maximum coincided with and increased the family 
maximum of July 28. Thence its decrease was even more rapid than 
that of Chironomus dispar, and its numbers were relatively less through- 
out the remaining period of study. 

Leiobunum politum Weed. Fig. 18, a. 

This harvestman, which was mainly a herb species, though rarely 
taken from the strata above and below, appeared in the collections to- 
wards the latter part of July, reaching its seasonal maximum the week 
of the twenty-eighth and after a slight decrease reaching another but 
lower summit the week of August 18. Thence the fall in numbers was 
rapid until the very end of the study, when a slight increase came, accom- 
panying rising temperatures and evaporation. 

Dicyphus famelicus (Uhl.) Fig. 20, Ca and b. 

This mirid was one contributing to the general aestival maximum. 
It appeared the latter part of July, and thence increased steadily in 
numbers until the week of August 25, when its maximum was reached; 
its numbers had declined abruptly a week later, when the last collection 
was taken. It was distinctly a herb stratal dominant, but at the summit 
of its abundance it appeared also in smaller numbers in the shrub stratum 
(C-a.). It feeds on Rubus (Britton, 1923), of which the herbaceous form 
triflorus was found here. 

Nabis sp. (juvenile). Fig. 20, B 

Nymphs of this genus were present in small numbers throughout 
the period of collecting, but reached a maximum about August 25, after 


62 ILLINOIS BIOLOGICAL MONOGRAPHS [426 


which they took part in the general decline of the following week. They 
were most abundant on the herb stratum, but were taken from the shrubs 
from time to time. 

Chironomus decorus Johann. 

This midge is included in its seasonal occurrence with the general 
population of Chironomidae. The general remarks about the family 
as a whole apply to it, as far as its seasonal and stratal distribution are 
concerned. 

Tanypus melanops Meig. 


The same is true in general, for this species, as was stated for Chirono- 
mus decorus and for the family as a whole. 


Tomocerus (Leaf) Society 


Tomocerus flavescens Tullberg var. separatus Folsom. Fig.17,b,c and d. 

This spring-tail, the only species found in much collecting in the habi- 
tat, isa permanent resident and a numerical predominant of the dead-ieaf 
stratum during the summer months. It is, however, sometimes found in 
small numbers in the ground (d), more rarely on the herb stratum (b). 
From its numbers it undoubtedly must work considerable change on the 
layer of decaying plant matter which makes up its real habitat. The 
fact that it was not taken in the first few collections was probably due 
to the fortuitous selection of an area where these animals were not found, 
such, for instance, as a very dry area. The maximum occurred on July 28; 
the following decline throughout the greater part of the collecting period 
is perhaps correlated with the gradual drying out of the leaf stratum, 
accompanied (d) by a partial migration into the soil, although the data 
is too scanty to more than suggest this. A very small rise in numbers 
came towards the very end of the study. 

Linyphia sp. (juvenile). Fig. 18, b. 

The population of young linyphiids showed in general the same course 
as the curve of the young epeirids, save that it developed more gradually 
despite its earlier start. The species first appeared early in July as strag- 
gling individuals, and gradually increased to a maximum the twenty-fifth 
of August, coinciding with the second maximum of the young Tetragnathas. 
There was a decrease and the evidence of a following increase towards 
the very end of the study. These were all young animals which would 
hibernate in the leaf litter. The maximum for the adults comes earlier, 
and the animals themselves are found in various situations higher up. 


Helodrilus (Soil) Society 
This was in general rather scantly populated for the period of study, 
and only a single predominant, a permanent resident, will be considered. 


427] A COMPARISON OF ANIMAL COMMUNITIES—BLAKE 63 


Helodrilus caliginosus trapezoides (Dugés) Fig. 17, A. 

The presence of this lumbricid is in itself an indication that the station 
studied is not wholly typical of coniferous forest, but has had its animal 
population modified by neighboring agricultural lands. The writer has 
never taken it in the primitive coniferous forest around Mount Ktaadn, 
and in general such forests are poor in Lumbricidae. It was thought of 
interest to trace the numerical fluctuations of this resident soil animal, 
in order to see to what degree they could be correlated with various physic- 
al changes. The curve includes both adults and juveniles, but more of 
the latter, since the method of collecting favored the escape of the adults. 

The first high point of the curve was that of the first date of collection, 
July 7. There had been previous rain, and the soil was wet, while the 
general condition of the forest floor was damp. Evaporation from the upper 
leaf strata continued rapidly and remained high for a period of weeks, 
during which the leaf and upper soil strata dried out appreciably; during 
this time the earthworm population of the upper soil, as judged by this 
single species, fell off as the animals retired deeper and out of reach of 
the collecting methods used. There was a slight increase July 21, corre- 
lated with the heavy rain of the period. The second and third apices 
correspond with the rainy weeks towards the end of the period of study, 
the difference between the two being probably unimportant, and due 
to the small local population of the quadrat selected for the second of 
these collections. 


DISCUSSION 


The coniferous forest habitat studied is a biotic environment of marked 
stratal differences in physical factors. These factors, in general, present 
a graded series from forest soil to forest crown, but the various strata 
fall into groups similar in conditions. These groups are: first, top soil 
and dead leaf strata; second herb, shrub, and high bush strata; third, 
low tree and high tree strata. The grouping is shown most clearly for 
evaporation. Since this is in itself a fairly reliable index of other phys- 
ical factors and since the evidence from data on temperature and humid- 
ity tends, as far as it goes, in the same direction, we may assume that 
grouping with steep gradients between is the general condition. The strata, 
divided on a basis of the physical conditions, fall into “groups subordinate 
to groups.”’ This is a suggestion of what has been pointed out, based on 
animal societies, for tropical forests by Brehm (1896). 

The cover of tall conifers is a dominant influence through the entire 
association. Even more important in any single member of the series 
are the stratal societies peculiar to each layer. These determine more im- 
mediately the physical and biotic conditions under which animals live. 
This point will be considered further in speaking of animal response. 


64 ILLINOIS BIOLOGICAL MONOGRAPHS [428 


If we consider these strata in order from below upwards, we find 
that the upper soil stratum presents an environment of comparatively 
low but very uniform temperatures, minimum evaporation and minimum 
light. The animals inhabiting this stratum as more or less permanent 
residents are those who reactions—and to some extent structure—are 
such as to find optimum conditions here: earthworms, the sparse mollusk 
population, ground and fungus beetles, and the larvae of a considerable 
number of other beetles and flies. 

In the next layer above, the leaf layer, conditions are somewhat 
less equable. Our only instrumental data are for temperature, which is 
higher and more extreme than in the soil. Light is somewhat greater, 
undoubtedly, and moisture less. The differences in animal population 
between the two are very considerable, both for quality and quantity, 
nor are the animals common to both as numerous as we should expect. 
The few individuals listed as found both in the ground and in the strata 
above the leaf must be considered either wholly exceptional, as in the case 
of Tomocerus flavescens, or caused by the presence of animals, such as 
the spiders, whose adult and juvenile stages are passed in different strata. 
The real population of the leaf stratum seems out of all proportion to 
the physical differences between it and the upper soil. Conspicuous is 
the predominance of many young spiders during August, while the maxi- 
mum of corresponding adult forms comes earlier and at upper strata. 

All the data available on the physical factors agree that between this 
leaf stratum and the herb stratum next above it occur the steepest gradients 
in the series for temperature, evaporation and probably light. Both 
temperature and evaporation show not only a great rise but also a very 
marked increase in extent of fluctuation. An animal moving from one 
of these strata to the other certainly undergoes a very considerable change 
in its physical environment. The number of species making this change 
is comparatively small. Further, such are again largely species of spiders, 
whose adults habitually occupy the upper strata, and whose young were 
taken at all stages of their downward migration toward winter quarters 
in the forest floor. A very few species may be noted which seem to change 
strata rather indifferently at the adult stage; an example is Camponotus 
herculeanus. The population of the herb stratum proper is large, and more 
varied than that of any other single stratum analyzed. Predominant 
groups of animals present were mirids, cicadellids, and various families 
of Diptera. 

The physical differences between the herb and shrub, while constant 
and by no means to be disregarded, appear to be of much less magni- 
tude than those existing between the last two strata considered. They 
are, however, in the same direction, involving increase of evaporation 
and light, and a corresponding increase of the fluctuations of these, and 


429] A COMPARISON OF ANIMAL COMMUNITIES—BLAKE 65 


probably other factors not measured. In other words, differences between 
physical conditions at herb and shrub levels are less decisive than those 
previously discussed. This is indicated not only by the instrumental 
data, but even more by the animal population data. A large number 
of animals are common to both strata. Among them are several of the 
predominants. The animals found in the present study only at shrub 
level constitute a varied list; the predominants are several species of 
Diptera, although no single species appears particularly prominent; 
the same status may be accorded also to the cicadellids and the aphids, 
considered as groups. 

The inhabitants of the forest above shrub level were not studied. 
We know from instrumental data that above this stratum, and especially 
beyond the tops of the low deciduous trees, the summer months show higher 
temperature, less moisture and greater fluctuation in both factors. If 
the inherent difficulties of a biotic study of this region could be over- 
come, the investigation would be very valuable, as it would give us the 
forms living in the evergreen foliage instead of the population of the decid- 
uous substratum. 

The animal population, as far as studied, shows a distinct division 
into stratal societies. This distribution seems to be determined by a com- 
bination of two factors; (1) physical differences between the strata; 
(2) biotic differences. For example, the alder-spittle insect was dominant 
in the shrub stratum, where belonged its food plant, a biotic factor; 
but a change in a physical factor, temperature, caused a downward, 
stratum to stratum migration. Other instances might be cited. It is 
probable that the physical factors become of greater importance at criti- 
cal seasons, such as the later fall. Weese (1924) gives evidence that the 
lowering temperature and temperature fluctuations serve as a stimulus 
causing forest-border beetles to migrate first into the interior of the forest, 
and then downward to the lower strata for hibernation. A downward 
migration of the young of many herb- and shrub-dwelling spiders is a 
well-known phenomenon of the later summer (Emerton). On the other 
hand, a very large number of phytophaga indicate by their vertical dis- 
tribution that the stratum in which they are found is determined by the 
presence of the host-plant. 

A study of the population shows that many of the species are forest- 
margin or deciduous underwood forms, rather than animals necessarily 
belonging to the coniferous forest habitat. Certain other species illus- 
trate the invasion of grassland forms, not found in such forests when 
remote from agriculture. 

The seasonal societies, because of the short and non-critical period 
when the collections were possible, are less marked than the stratal socie- 
ties. For the greater number of species, however, and especially for the 


66 ILLINOIS BIOLOGICAL MONOGRAPHS [430 


predominants, the evidence indicates an early summer (Aestival) maxi- 
mum, the peak of which had passed at the time the collections were begun, 
or a late summer (Serotinal) maximum, developing during the latter 
period of study. 


SUMMARY AND CONCLUSIONS 


The coniferous forest habitat studied shows a very regular stratifica- 
tion of the physical factors of environment; this is most conclusively 
proven for evaporation, but is in general true for all physical factors. 

The evaporating power of air increases with elevation above the 
forest floor. Based on this factor, the habitat could be divided into three 
main strata, and each of these into two or more sub-strata.. 

Temperature increases and humidity decreases in the upper strata, 
while both show greater range. These results, however, are less con- 
clusive than those bearing on evaporation, and show less stratal difference. 

Light intensity increases markedly upward from the forest floor. 
Its gain in successive layers of deciduous undergrowth is almost compar- 
able to the rise in evaporation. 

Biotic response to these conditions is expressed by the composition and 
distribution of the animal stratal societies. This response, however, is com- 
plicated in the various strata by the presence of influences which are them- 
selves biotic. The ultimate reponse of the animal, at least during summer, is 
evoked by the combination of physical and biotic factors. 

Physical factors are responsible for stratification in proportion to 
their intensity. During summer conditions in temperate climates, biotic 
factors tend to attain greater importance. During critical periods of 
climatic and physical stress, the situation is reversed. Thus under mon- 
tane conditions, as seen in the Ktaadn studies, physical factors may be 
dominant at all seasons. 

A seasonal series of societies as well as a stratal one, was shown by the 
animals of the area studied. Numerically the animal population, as a 
whole, displayed two high points—one in late spring, and another in late 
summer. These two maxima were not due to the appearance of a second 
apex for species reaching a high point in the vernal society. Among insects 
generally, they were caused by the appearance of different species; among 
spiders generally, by two distinct phases in the life history. 


431] A COMPARISON OF ANIMAL COMMUNITIES—BLAKE 67 


THE ANIMAL ECOLOGY OF DECIDUOUS FOREST 
IN WINTER 


SCOPE OF WORK 


This portion of the study was undertaken in an attempt to secure 
data on the animal population of deciduous forest in winter, with special 
reference to its stratal distribution. It was carried on in the same local- 
ity and by the same methods, as the study of Weese (1924), made in 
part during the winter of 1921-1922. It should give us an idea of the 
differences existing between the animal communities of a locality during 
the same season in different years, when examined by the methods of samp- 
ling. Since this study was made in winter, the predominants varied greatly 
from those based on a complete annual cycle, and the animals present 
in the largest numbers were the permanent inhabitants of the forest- 
floor strata; second in importance are the hibernating animals whose 
stratum of summer activity is higher in the forest, or outside the forest 
altogether. It should be understood that the data presented is distinctly 
that of a winter study. It does not give seasonal societies, although it 
indicates the passing of the last of the autumnal society into the hibernal 
one; its principal emphasis falls on the response of the animals of the 
winter society to changes in climatic conditions. 

The study was continued to include the prevernal society; the re- 
sults of this portion of the work will be presented at a later time. Certain 
groups of animals have not been included in the present report because 
of the impossibility of getting determinations on them in time; these 
include the Cicadellidae and some larvae. 

The generally neglected dynamics of the hibernal society is dealt with 
in detail because of the following facts: 1, Winter survivors are the basis 
of increments to the population during the warmer months which follow; 
2, winter conditions have important relations to—a, survival and b, 
rate of development in spring. The neglect of the study of this phase 
of insect activity in particular, is responsible for much confusion in econom- 
ic entomology, and the same may be true for other groups of animals. 

In addition to the quantitative study of the invertebrates an attempt 
was made to take a census of the winter birds and some general observa- 
tions were made of the mammal population; no reptiles or amphibians 
were observed during the study. 


68 ILLINOIS BIOLOGICAL MONOGRAPHS [432 


ENVIRONMENT 

This has been thoroughly described by Weese (1924) and its plant 
communities by McDougall (1922); these papers should be consulted. 
The local area embraced in the instrumental study and from which the 
collecting was done was practically identical with that of the first author. 
Collecting was commenced before the leaf-fall from shrub and herb strata; 
most of the ground was carpeted with a rather thin layer of organic debris. 
By November 6 many of the leaves had fallen from these strata, and.a 
thick layer carpeted the ground. Not until December 22 was the leaf 
stratum frozen and the soil stratum partly so. On December 29 both were 
well frozen and covered with a 2 cm of snow, which had increased in thick- 
ness to 15 cm by January 5, and to 17 cm by the week following. By 
January 26 the snow had decreased in thickness to about 12.5 cm, and 
it remained thus for the next week. A sudden thaw on February 9 left 
the leaf and soil strata bare and very wet. This condition lasted through 
the next three weeks, but on March 2, the day of the last collection, 
leaf and soil strata were again frozen and covered with 5 cm of snow. 
The general appearance of the habitat during the greater part of the period 
of study is shown in Fig. 5. 

The winter period is of course the time when all animals of terres- 
trial communities in temperate regions show inactivity as a response, 
at least in part, to the stressful climatic conditions. Under montane 
conditions this inactivity is probably absolute, as far as the inverte- 
brates are concerned, and lasts during the long period when the ground 
is covered with snow and the shallow soil is frozen to the underlying rock. 
Under the less severe conditions found in northern coniferous forest, 
the snowfall is none the less heavy and long and the autumn freezing 
deep; the result is probably a practically quiescent condition of the ani- 
mal population of the ground strata, perhaps as marked as that of montane 
tundra and forest. In the more temperate conditions where deciduous 
forest is the vegetation climax, the winters are less severe and the animal 
population of the forest floor shows a week to week fiuctuation with the 
changing climatic conditions (Weese). In order to measure these climatic 
changes, for comparison with the accompanying biotic fluctuations men- 
tioned above, a number of recording instruments were employed, their 
exposure being similar to that of Weese’s instruments. 

Temperatures were recorded at three levels. A thermograph was 
placed in a standard instrument shelter about 0.6 m above the ground 
in practically the same spot where Weese’s 0.6 m instrument was exposed. 
This also sheltered the clock and recording apparatus of a distance thermo- 
graph, whose sensitive bulb was buried under 5 cm of dead leaves and 
10 cm of top-soil. Another thermograph was exposed at a height of 11 m 
in a maple tree nearby. A standard Weather Bureau type maximum 


433] A COMPARISON OF ANIMAL COMMUNITIES—BLAKE 69 


and minimum thermometer was also placed in the instrument shelter; 
by this all the other instruments were set and checked. The changing 
of charts and treatment of the data gained therefrom was precisely like 
that employed in the coniferous forest study, save that the soil thermograph 
charts were graduated in degrees Centigrade, and therefore did not need 
the conversion which was employed on the other two. The tree instrument 
was started the week ending November 17, and its record contains one 
break, that occurring during the week of January 12. The other two 
instruments were started the week following. All three records, for the 
purposes of this report close with the week ending March 9. The results 
of the study appear in Figs. 21 and 22. 

If we consider the air temperature 0.6 m above the ground we see 
that, starting on November 24, there was a sharp decline the following 
week, followed by a considerable rise. The next two weeks showed very 
slight depression but the week of December 29 brought the sharpest 
change and lowest temperature of the study, the mean temperature 
falling to -14.2°C. From this date until February 9 the general trend 
is upward sometimes by sharp changes; then occurs another depression, fol- 
lowed on February 23 by a rise to the highest point attained by this 
instrument since the beginning of the study; thence the temperatures 
fell off gradually until the end. 

The record of the instrument in the tree accompanies irregularly 
that of the lower station, crossing from side to side, but, with a few ex- 
ceptions, lower with falling temperatures and higher with rising ones. 
In other words, the temperature at the higher level makes more response 
to climatic changes, is more extreme. A reversal of temperatures takes 
place the week of December 8 with falling thermometer, and a second 
the week of March 2. Reversals on rising temperatures occurred during 
the weeks of January 5 and March 9. 

The records of soil temperatures were not begun until after the fall 
overturn, or reversal of temperatures between earth and atmosphere; 
at this time it was already higher than the temperature of the air. With 
the exception of a slight rise for the week of December 15, the trend was 
steadily downward until January 12, the earlier fall being sharper than 
the later ones. The maximum depression of air temperatures for December 
29 affected the soil not at all. The trend from January 12 until the end 
of the study was upward, gradually at first but later more markedly. 
The final week of the record shows another slight depression, following 
marked depressions of atmospheric temperature for the week preceding. 
With the exceptions of the two warm weeks of February 9 and 23, the 
soil temperature was above the air temperature throughout the period 
of the study. It was little affected by atmospheric temperature extremes 
in either direction. 


70 ILLINOIS BIOLOGICAL MONOGRAPHS [434 


If we now consider the temperature ranges at the different strata, 
we see that they show more plainly what was indicated in a general way 
the actual temperatures, that is, that the extent of range increases from 
the ground upward. From the soil to the atmosphere this is of course 
very marked; the curve of temperature range for soil never even approaches 
that of the air strata. The relations between the temperature ranges in 
the two air strata are less clear, and the curves show more crossing; 
but the upper stratum, 11 m above the ground, showed on the whole 
a greater range than the lower, 0.6 m above the ground, and this was 
decidedly marked for the weeks of highest temperatures. (Fig. 22). 

If we compare this data with that taken by Weese in the same stations 
in 1921-1922, we see a similar type of curve for the same period of the 
year, consisting of a depression to a minimum point, followed by a general 
upward movement. ‘The early winter fall of temperatures was some- 
what less regular, and the low point was not reached until the early 
part of February. The minimum was not so low, and the subsequent 
rise was not so sharp as in 1924-1925. The winter of 1921-1922 was cer- 
tainly the warmer and somewhat the more uniform of the two. 

The relative humidity of the air during winter is probably of much 
less importance than the temperature, since the latter was so low as to 
cause freezing of the ground strata during most of the period of study. 
Even when the ground remained unfrozen the air temperatures were 
so low that most of the animal population remained, as will be seen, 
in the ground. Since, however, any factor must be known before it can 
be ignored, the relative humidity was taken throughout the period of 
study. The hygrograph used in its measurement was placed in the ins- 
trument shelter 0.6 m above the surface of the ground. The sheets were 
changed, and the computations made as in the coniferous forest study. 
The data obtained is given in graphic form in Fig. 23. It will be seen that 
the curve of mean relative humidity does not show any very striking 
points for the period of study. Its lowest points fall in the dry portion 
of the late autumn, while the region of its highest general average falls 
during the periods of rain and thaw in February. The curve of daily 
variation is high and irregular during the early part of the study but 
falls rapidly during the winter, and shows less variation from week to 
week. With rising temperatures the range of atmospheric humidity also 
increased, but its weekly variations did not, at the end of the time covered 
by this report, again attain those of the late fall. It seems unlikely that 
humidity differences of the order shown, when accompanied by such low 
temperatures as existed, could be of much importance in determining 


the winter distribution and fluctuation of the animal population in the 
leaf and soil strata of the ground. 


435] A COMPARISON OF ANIMAL COMMUNITIES—BLAKE 71 


From this it will appear that the changes in the population of hiber- 
nating animals in the forest-floor are more probably influenced by the 
changing temperatures than by any other physical factor. The nature 
of the population, its stratal and weekly distribution and its predominant 
species will be considered next. 


THE BIOTA 


The population sampling was done in the same way as in the conif- 
erous forest study, save that during the period when the ground was 
frozen the upper 10 cm of soil of a quadrat, which alone were examined, 
were removed entire and examined for the animal population after thaw- 
ing, instead of being gone over in the field. There is nothing in the data 
to indicate that the use of two methods in examining this stratum has 
caused any discrepancies in its record. The results of the quantitative 
part of the study, as a whole and by strata, are shown as graphs and in 
tabular form (Table XX). Fig. 24 shows the entire population curve, 
the separate curves of shrub and herb populations. Fig. 25 gives separately 
the curves of the leaf and soil animal populations. The weekly collection 
and analysis of stratal ‘‘samples’”’ of animal population was begun several 
weeks earlier than the instrumental observations. 

Beginning with the week of October 9 we have a series of weekly 
fluctuations, some of very considerable magnitude, lasting until the 
early part of December. The general mean of these shows, however, a 
somewhat downward trend, despite the rather high points reached on 
alternate weeks during late November and early December. The first 
high point reached was that of October 13. Thence there was a sharp 
drop to October 27. From this time on until instrumental readings were 
begun the fluctuations seemed to be determined largely by the air tempera- 
ture, but to some extent were correlated for the lower strata with amount 
of moisture in the leaves and soil. For example, the collection of October 6 
was taken on a cool day; October 13 was warm and sunny; November 
10 showed an air temperature of 13°C. when the field work was done, 
while the following week, when the smallest collection to date was ob- 
tained, the temperature had fallen to 1°C, and there were flurries of snow. 
Beginning with November 24, the population curve falls with falling tem- 
perature during the next week, and rises with rising temperature the week 
following. The sharp drop in animal population during the weeks of De- 
cember 8-22 was apparently caused in part by gradually falling tempera- 
tures in the soil and in part by the dry condition of the leaf and soil strata; 
the great drop in air temperature did not come until a week later. Begin- 
ning with December 22, the total population trend is upward, though 
many fluctuations, until almost the end of the study. The population 
apices roughly coincide with temperature apices, especially where these 


72 ILLINOIS BIOLOGICAL MONOGRAPHS [436 


last were unusually high. At the very close of the period of study the pop- 
ulation fell sharply to the very minimum observed; this accompanied a 
temperature fall, moderate in amount but very sudden, from one of the 
highest points observed during the whole study. 

The population as a whole appeared to fluctuate in numbers with 
climatic changes, especially temperature. Air temperatures seemed to 
be of more importance during the early part of the study, when more 
of the population was in the shrub and herb strata. Later changes of 
atmospheric temperature were less directly active on the animals, now 
almost exclusively confined to the forest floor. Exceptions appeared 
where sudden and extreme fluctuations of temperature, such as that 
of February 9, were sufficient to affect directly the temperatures of the 
forest-floor strata; this seemed more likely to occur on rising tempera- 
tures. It might be recalled that the sensitive element of the soil ther- 
mometer was buried at the lower limit of the lowest stratum sampled. 
The leaf stratum was more nearly exposed to the air, and more responsive, 
we must suppose, to changes in air temperature. There is biotic evidence, 
as will be seen, that this is so. 

The shrub society as might be expected, was of importance only in 
the earlier part of the study. It contributed especially to the popula- 
tion apex of October 13, less to the lower apex of November 10. Thence 
the data for this stratum are based on a few hardy individuals and species 
which ventured out of hibernation during an unusually warm period. 

The herb society curve roughly accompanied that of the shrub; differ- 
ences between the two are probably fortuitous and due to the chance 
selections of comparatively well or poorly populated areas for sweeping 
on the various dates. After October 27 this stratum makes no important 
contribution to the whole population, and its occurrence at all in the record 
is determined by the same conditions given for the shrub animals. 

A glance at the leaf society (Fig. 25) shows at once that after November 
10 the population of this layer became the determining factor in the whole 
number of animals in a sample. Its curve follows closely and falls little 
short of coinciding with, the general population curve. Its predominants 
are the predominants of the winter population, and with very few excep- 
tions were the only animals found in any numbers during the study. 
This is natural when we consider that of the two strata which are of 
importance in a winter study, this is the one most directly affected by 
climatic changes, especially in the matter of receiving warmth with ris- 
ing temperatures. The curve for this society shows two groups of peaks 
preceded, separated and followed by low points. The earlier low portion 
of the curve, during the month of October, is probably due to the dry 
condition of this layer and the retreat of its population deeper into the 
soil. Indeed, the high value of the soil collections on some of these dates, 


437] A COMPARISON OF ANIMAL COMMUNITIES—BLAKE 73 


the highest found for the soil stratum throughout the study, is strongly 
suggestive of such a downward migration. With the fall rains and before 
the coming of extremely low temperatures, the curve for this stratum 
mounted higher and with minor fluctuations due probably to tempera- 
ture, remained high until December 8. It then took part in and largely 
determined the great descent of population during the two following weeks, 
which has been already discussed. In fact, from this point on its story 
would be that of the population as a whole, of which it made by far the 
greater part. 

The soil population was the most uniform of the animal societies. 
Its early high points have already been discussed. Its high points during 
the winter, none of which are so marked as to be entirely above suspicion 
as caused by the selection of unusually good quadrats for collecting, 
do nevertheless show apices which generally coincide with the apices for 
the leaf stratum. The most important exception to this is the collection 
of February 9, where the lowest soil pupolation of the study occurred 
coincidently with the highest leaf population. This was one of the most 
marked temperature fluctuations observed, and perhaps called into activ- 
ity in the leaf stratum a larger proportion than usual of the animals us- 
ually remaining in the soil. There is nothing to indicate that the upper 
10 cm of soil examined serves during colder weather as a retreat for ani- 
mals otherwise found in the leaf stratum on the surface. If this were 
the case, the soil curve would rise as the leaf curve falls. There is no 
evidence of this. Obviously the animal population of the leaf stratum, 
on the approach of freezing temperatures, migrates downward toa point 
below the 10 cm level and probably below the frost line, which was not 
deep at any time. 

At the same time it should be noted that the animals found hiber- 
nating in the forest-floor showed, practically without exception, a complete 
absence, as far as could be observed, of harmful effects of low tempera- 
tures. Throughout the greater period of the study the leaf layer was 
frozen, and the upper portion of the soil more or less so, and frequently 
frozen as hard as ice. Animals of all sorts, mollusks, myriapods, arachnids 
and insects, when thawed out of the leaves or the solid masses of frozen 
soil moved about actively and seemingly with vitality unimpared. There 
was nothing in their appearance or behavior to indicate any marked 
winter mortality. Under these conditions of cold and freezing neither 
decomposition nor destruction by scavengers could take place, and it 
seems safe to infer that the scarcity of intact dead animals, coupled with 
the uniform activity of the live animals when thawed out of the frozen 
matrix, indicates that the death-rate among hibernating invertebrates 
frozen in the forest-floor is not as high as has been supposed. Of course 
many animals habitually pass the winter below the frost-line; such ani- 


74 ILLINOIS BIOLOGICAL MONOGRAPHS [438 


mals would be presumably destroyed or at least debilitated by exposure 
to freezing temperatures. The above remarks apply, however, to the ani- 
mals normally found hibernating in the forest above the freezing level, 
and the observations on which they were based were made in what was 
an unusually severe winter for the locality. 

To summarize the winter activities of the animal societies we might give 
a general account of what happened during the present study. At the time 
when collecting was commenced, the total population had fallen much 
below the autumn maximum caused by the influx of forest-border species 
coming in to hibernate in the shelter of the forest (Weese). There remained 
still, however, some evidence of this in the case of individual species. 
The animals left on the shrubs and herbs were few, and rapidly became 
fewer, crawling for shelter into the leaves and soil. The resident popula- 
tion of the soil and leaves, moisture-requiring and dark-choosing (Shelford, 
1913) invertebrates, were few in number to the depths collected, but 
appeared more numerous than usual in the soil and correspondingly less 
so in the leaves. With the increase of available moisture in these lower 
strata, and before the ground was much affected by the chilling of the 
air, the population of invertebrates, largely residents in the leaf layer, 
rose, and with minor fluctuations remained high for a period of weeks. 
It then rather abruptly decreased with the chilling and possible with 
the drying of the leaf layer. The minimum point of population preceded 
the minimum point of air temperature by a week. From this time on the 
population, now consisting almost wholly of the leaf stratum animals, 
rose gradually, though fluctuating from week to week, until February 9, 
when a warm rain cleared away the snow and thawed the frozen soil and 
leaves. The population mounted at the same time to the largest total 
observed in the study. A lower temperature followed the next week, 
and the number of animals fell to less than half, presumably mostly re- 
treating into the earth deeper than the samples were taken, though there 
is evidence that a few remained in the surface soil. A second high point 
the following week accompanied another rise in temperature; this was 
still caused by numbers of animals appearing in the leaf stratum. With 
the sharp fall of temperatures the week following the leaf and total popula- 
tions dropped almost to il, most of the animals reéntering the deeper 
layers of the soil, but a few remaining in the upper 10 cm. Throughout the 
period the soil population had undergone the least fluctuations. The 
warmest days had brought up a few animals to the herb and shrub strata; 
these disappeared with the falling temperatures. 

The animals named as predominants below must be considered as 
entitled to that term only with reservations; that is, they are numerical 
predominants, the most numerous animals found in the area at the time 


439] A COMPARISON OF ANIMAL COMMUNITIES—BLAKE 75 


the study was made. Second, they are seasonal predominants in part; 
some of the species listed would not be found in the deciduous forest 
floor save at the season of hibernation. The most numerous species, 
however, are permanent residents of the lower strata of this habitat. 
With these reservations in mind and with the repetition of the statement 
that most animal predominants do not “control the habitat” as some plant 
predominants do, we may consider the species listed as good and valid 
seasonal and stratal animal predominants. Some of them are more than 
this. 

The following species are listed by their stratal occurrence and the 
invertebrates are given in their respective socies in order of their relative 
abundance; the seasonal and in some cases the stratal distribution is 
plotted for most of the species in the plates. 

Subinfluents: 

Tomocerus (Leaf) Society: Enchytraeidae (undetermined), Tomo- 
cerus flavescens Tullberg var. americanus Schott, Onychiurus subtenuis 
Folsom, Carychium exiguum (Say), Malihodes cp. (larva), Telephanus 
velox Hald., Lygus pratensis oblineatus (Say), Isotoma sp., Vitrea indentata 
(Say), Anyphaena rubra Emer. (juvenile), Cleiodogona caesioannulata 
(Wood) (juvenile), Leptothorax curvispinosus Mayr., Zonitoides minus- 
cula (Binney), Gastrocopta tappaniana (C. B. Adams), Dictyna volupis 
Keyserling, Nitidula rufipes (L.), Phalacridae (undetermined), Zoni- 
toides arborea (Say), Carycium exile H. C. Lea, Nabis ferus (L.), Leptocera 
sp., Linotaenia chionophila (Wood), Scytonotus granulatus (Say), Tipula 
sp. (larva), Phyllotreta sinuata (Steph.), Meracantha contracta (Beauv.) 
(larva), Myodochus serripes Oliv., Cantharis sp. (larva), Fannia sp. (juve- 
nile); Peromyscus leucopus novaboracensis (Fischer), Blarina brevicauda 
(Say), Sylvilagus floridanus mearnsii (Allen). 

Fontaria (Top-soil) Society: Lasius flavus Fabr. subsp. nearcticus 
Wheeler, Fontaria virginiensis Dry., Pokabius bilabiatus (Wood), Ony- 
chiurus armatus Tullberg, Onychiurus fimetarius (L.), Ptilodactyla serri- 
collis (Say); Scalopus aquaticus machrinus (Rafinesque). 

A few species are listed which appeared at the beginning of the collec- 
tions in the 

Linyphia (Herb) Society: Linyphia phrygiana C. Koch, Lathrididae 
(undetermined), Tetragnatha sp., Epitrix brevis Sz. 

A single mammal was noted as characteristic of the winter. 

Sciurus (Tree) Society: Sciurus niger rufiventer (Geoffroy). The above 
lists include only a small proportion of the species taken in the weekly 
collections; they do, of course, include all species taken in such numbers 


as to entitle them to status as predominants in the socies where they 
occur. 


76 ILLINOIS BIOLOGICAL MONOGRAPHS [440 


Predominants of the Tomocerus (Leaf) Society 

Enchytraeidae (Fig. 30, Bc and d. 

This family of worms, on which it was not possible to secure determi- 
nations, was decidedly a predominant group in the leaf society, where 
they appear to be characteristic animals (Welch, 1914). They are con- 
stant residents, but may withdraw into the soil if conditions become 
unfavorable. They were found in the leaf layer during the early collect- 
ing, but seemed to retreat into the earth when the ground became drier 
during the fall, becoming very scarce in the collections until the late 
rains. They then became numerous in the leaves and fairly so in the soil, 
their numbers contributing much to the high populations of November 
24 and December 8. With falling temperatures they became few in the 
leaves, some apparently lingering in the top soil, and finally disappeared 
from the collections altogether. They appeared again during the warm 
and wet week of February 9 and make up a notable part of the high curve 
for that date, disappearing almost completely with the low temperature 
and general population decline of the following week. They again became 
abundant the week following, and disappeared entirely during the cold 
Monday when the last collection was taken. From the numbers of the 
animals that may be found in the dead leaf layer during warm and wet 
weather, it may be that we have here not only a numerical but also a 
real stratal dominant, the gross effects of whose activities on the grad- 
ually decaying layer of organic debris may be considerable. 

Tomocerus flavescens Tullberg var. americanus Schott. Fig. 30, Ab, c 

and d. 

The seasonal and stratal distribution of this spring-tail is very suggest- 
ive of that of the Enchytraeids. In fact, its close agreement with those 
animals in its reponse suggests an analogy to the “behavior agreement” 
found by Shelford for aquatic and terrestrial animals (1913, 1914). The 
animal seems to be somewhat more tolerant of unfavorable conditions, 
however, remaining in the leaves and top soil in considerable numbers 
during periods of freezing, from which it emerges into activity, at least, 
unimpaired. It was rarely taken on the herbs. It seems likely that in 
this species, as well as in the other numerous Collembola, we may have 
real stratal predominants. Their numbers, constant presence and food 
‘habits suggest that the part they play in the organic changes going on 
in the forest-floor may be by no means as small as their size and lack 
of ‘economic importance” in the usual sense might lead one to suppose. 

Onychiurus subtenuis Folsom (Fig. 29, bottom curve). 

This species appeared for the first time with the rising temperature 
of January 5. Thence it fluctuated in small numbers until February 9, 
when it took an important part in the maximum of that date. Along 
with other species, it fell off sharply the following week, but, unlike most 


441] A COMPARISON OF ANIMAL COMMUNITIES—BLAKE 77 


others, it disappeared completely the warm week following, when most 
other species took more or less part in the second population rise. It 
might appear that we have here a less hardy species than Tomocerus 
flavencens which, called out of deeper hibernation by the unusually warm 
weather, was chilled back during the following cold snap, from which 
it was unable to recover. 

Carychium exiguum (Say) (Fig. 26, I). 

This snail was present in the largest numbers of any mollusk, but 
neither it nor any of the remaining forms was in the same order of abun- 
dance as those just named. It was present in the leaf layer in moderate 
and fluctuating numbers from the time of the autumn rains and conse- 
quent moistening of this layer until the end of the study. Its single high 
point coincides with the second population apex of February; it increased 
only slightly at the time of the first and greatest February rise. Inasmuch 
as these were periods of both increased soil moisture and rising tempera- 
ture it would be difficult to assign to either the rise, which was general 
for several species of mollusks; but the general habits and responses 
of the animals leads one to suspect the former. 

Malthodes sp. (larva) (Fig. 28, E) 

This cantharid larva was the most abundant beetle; it appeared 
early in the collections and with increasing frequency and in increasing 
numbers as the study progressed. Its first marked increase came with 
the slight but distinct population rise that followed the low week of De- 
cember 22. Its second maximum, curiously enough, falls on the week 
of moderately low temperatures that intervened between the two high 
weeks in February. 

Telephanus velox Hald. (Fig. 28, Db, c, and d.) 

This species is of particular interest as studied in detail by Weese 
in 1921-1922. He found it on the herb stratum October 3, and in the 
leaf stratum throughout the winter, with a maximum on November 7. 
Save that the hibernation migration took place later, the findings for 
the beetle in 1924-1925 were remarkably similar. It was swept from the 
herbage October 13, and showed an extraordinary maximum in the leaf 
stratum on November 24. Thence it appears in varying numbers all 
winter, its only other marked increase coinciding with the first “high”’ 
in February. This species was also taken in the ground from time to time 
and its appearance there in some numbers preceded the February rise. 

Lygus pratensis oblineatus (Say) (Fig. 27 Fa, b, c and d.) 

The tarnished plant bug appeared in considerable but varying numbers 
throughout the study, but for the winter seasonisundoubtedly to be classed 
in the leaf society. It appeared in increasing numbers on the shrub 
and herb strata during the early part of the study, disappeared from these 
strata in the order named and became abundant in the leaf stratum, 


78 ILLINOIS BIOLOGICAL MONOGRAPHS [442 


where its numbers underwent considerable fluctuations from week to 
week. Its first and greatest increase there coincided with the general 
rise following the period of lowest populations. Thence its numbers fell 
off sharply and then with rising temperatures gradually increased until 
February 16, its high points not exactly coinciding with the highest 
temperature points. On the date when the highest temperatures occurred, 
however, a few individuals appeared in the herb and even ascended to 
the bare shrubs. A few individuals also appeared in the soil early in the 
season. The fall distribution of this insect among the strata indicated 
an inward migration from the forest border, followed by a downward 
migration into the leaves, similar to that described by Weese for several 
species of forest-border beetles in this same habitat. 

Tsotoma sp. (Fig. 29, Cc and d.) 

This spring-tail appeared in small numbers in the soil about December 
29, and a few were taken in the leaves February 2. The great rise took 
place on February 23, and took part in the general high curve for that 
warm period. Its numbers at once declined, and it was not taken again 
in the collections. 

Vitrea indentata (Say) (Fig. 26 Hc and d). 

This snail was found throughout the winter in hibernation in the 
leaf layer; its fluctuations during the early part of the season are prob- 
ably not significant. At the time of the coldest week, the animal dis- 
appeared from the leaf stratum but was taken in some numbers from the 
soil. The maximum for the winter fell on the“‘high” of February 23, and 
was probably determined chiefly by moisture. 

Anyphaena rubra Emer. (juvenile) (Fig. 26, Ca, b, c.) 

These young clubionids hibernate habitually in the leaf stratum, 
where they were taken in varying numbers throughout the winter. Their 
records of stratal occurrence show a downward migration from shrub 
and herb strata to the leaves, during the whole autumn period. Afewspeci- 
mens were taken from the herb level on warmer days during the winter. 

Cleiodogona caesioannulata (Wood) (juvenile). (Fig. 31 Cc, d) 

This diplopod is a characteristic species of the animal society inhabit- 
ing the humus and ground litter on the deciduous forest floor (Adams, 
1915; Weese, 1924), where it exercises subinfluence in altering the com- 
pounds produced by plant decay (Adams, loc. cit., and reference to Cook 
(1911c). It appeared in the samples taken by Weese during July and again 
in early November. In the writer’s collections, Cleiodogona appeared 
first in the soil stratum on November 17, in the leaf stratum the week 
following (when it was not taken in the soil), and it increased in numbers 
in the leaves through the week following, reaching the high point for 
the collections on December 8. The following week the species disappeared 
entirely from the leaf stratum but were still present in considerable numbers 


443] A COMPARISON OF ANIMAL COMMUNITIES—BLAKE 79 


in the soil. They then disappeared entirely from the collections until 
the warm week of February 9, and for the next two weeks they were 
taken in some numbers in the leaves. The cold week of March second 
yielded none of these animals in the leaf stratum, but a considerable number 
remained in the upper 10 cm of soil. They were not taken again during 
the study. This species, as far as its stratal distribution is concerned, 
seems to behave like some of the mollusks. It was absent from the upper 
strata during the dry weather of the fall both in 1921 (Weese) and 1924. 
It reached its maximum when the forest floor was moist from the late 
autumn rains, and disappeared during the coldest part of the winter. 
Early spring rains and warm weather brought up numbers of these ani- 
mals into the forest floor litter, but with falling temperatures they passed 
into the soil and thence into deeper hibernation at levels where they were 
not reached by the methods of collecting. 

Leptothorax curvispinosus Mayr. 

This ant is an example of a resident stratal predominant; maxima 
represent colonies of hibernating individuals which chanced to be in the 
quadrats selected for study on the dates in question. They are included 
because they represent a fairly numerous and characteristic species and 
suggest the discontinuous distribution of animals with such mores over 
the forest floor. 

Zonitoides minuscula (Binney) (Fig. 26, G) 

This land snail was collected in fluctuating numbers from the leaf 
stratum during the entire winter, not appearing until after the fall rains. 
The first rise in numbers was that of December 8, and was a part of a 
general population high, accompanied by a considerable rise in mean 
temperature; the second high point coincided with that of Vitrea indentata 
and was no doubt due to the same factor. 

Gastrocopta tappaniana (C. B. Adams) (Fig. 26, F) 

This species showed a rather different type of distribution from that 
of the species just described. It showed a high point early in the season, 
probably correlated with the moisture incident on the autumn rainfall, 
and then disappeared entirely from the collections until the “highs” 
of February, when it was again sparingly taken. 

Dictyna volupis Keyserling (Fig. 26, B-a-b, and c.) 

These young Dictynids showed the same stratal and seasonal dis- 
tribution as Anyphaena rubra, already described, save that they did not 
appear above the leaves on the warm days in the latter part of the winter; 
they sometimes do so, however (Weese, 1924). 

Nitidula rufipes (L.) (Fig. 28, C). 

This species was found hibernating in varying numbers in the leaf 
stratum throughout the winter; it responded to the conditions existing 


80 ILLINOIS BIOLOGICAL MONOGRAPHS [444 


on February 9 and 23 by appreciable increases in numbers, no doubt 
called forth from deeper hibernation. 

Phalacridae (undetermined) 

The numbers and seasonal and stratal distribution of these beetles 
indicated the same inward and downward migration described by Weese 
for Phalacrus politus in this habitat; they appeared first on the shrubs, 
later on the herbs and thereafter and throughout the winter in hiber- 
nation in the leaf stratum. In the absence of specific determinations, 
their occurrence has not been further studied. 

Zonitoides arborea (Say) (Fig. 26, E) 

This species was taken only towards the latter part of the study and 
its only marked increase in numbers fell on February 23, the period when 
most of the mollusks showed a high point. 

Carychium exile H. C. Lea (Fig. 26, D) 

The appearance of this snail in the collections agrees well with that 
of Gastrocopta tappaniana but with no other species of mollusk found 
in any numbers. Its maximum fell in the late autumn, and was probably 
determined by moisture, but it did not appear again in the collections. 
It was found exclusively in the leaves. 

Nabis ferus (L.) (Fig. 27 E-a, b, c and d). 

Save that it was present in smaller numbers, this common nabid show- 
ed the same distribution in the collections as the tarnished plant bug; 
it appeared in the fall on herbs and shrubs, passed into the leaf stratum, 
and there remained throughout the winter, a few specimens being also 
taken from the soil from time to time. Like the plant bug and many 
other animals it appeared in small numbers above the leaves during warm 
periods in the latter part of February. 

Leptocera sp. (Fig. 31, F-a, b, c, d). 

This borborid appeared first in the collections at shrub level on Oc- 
tober 6, and other individuals of the same species were taken in the herb 
society for this date. By the next week it had disappeared from the shrubs, 
but was present in increased numbers among the plants of the herb stratum. 
Here it appeared for the last time on November 10. It was collected 
in numbers from the leaf stratum on November 24, but disappeared with 
the falling temperatures of the week following. The temperature rise 
of December 8 was accompanied by considerable numbers of these flies 
in the leaf society. The following week they had disappeared from theleaves 
but a few were found in the soil. They were not taken thereafter. The 
data suggest a downward migration similar to that observed for other 
species, accelerated by falling temperatures and arrested by rising ones, 
to the level of hibernation. Weese took Leptocera evanescens Tuck. from 
ground and herb strata at various times through the winter of 1921-1922. 


445] A COMPARISON OF ANIMAL COMMUNITIES—BLAKE 81 


Linotaenia chionophila (Wood) (Fig. 31, A-c, d). 

This centipede was a common animal of the leaf society during the fall. 
It appeared first in the soil collections, perhaps because of the dryness 
of this stratum during the early part of the study. Thence on it was 
common in the leaf stratum until the temperature drop of December 1, 
when it disappeared from the collections for the next two weeks. On 
December 15, when the temperature of the soil had risen somewhat, 
a few appeared in the soil stratum, and a few more were collected in the 
leaves during the warm week of February 9. Weese found this species 
on the forest floor from time to time during the winter. 

Scytonotus granulatus (Say) (Fig. 31, E-c, d). 

This millipede was a characteristic animal of the leaf stratum, from 
which it was collected in varying numbers from time to time during the 
period of study. Its periods of abundance appear to coincide with even 
or slightly rising ground temperatures. Specimens were collected from 
the soil stratum during the latter part of November, but except for this 
was a leaf-stratum form. Its habitat relations are no doubt similar to 
those of the other diplopods discussed. 

Tipula sp. (larva) (Fig. 27, Dc, d) 

Crane-fly larvae of the genus Tipula were fairly common in the leaves 
and soil during the fall and late winter. They reached their maximum 
numbers in the “high’”’ of February 23; there is some evidence that they 
migrated a short distance into the upper soil during the following cold 
week and again returned to the surface leaves the next week, which was 
warm. With the return of extreme temperatures at the end of the study 
they disappeared, no doubt going to the deeper layers of the soil where 
they had passed the extreme part of the winter, and where they were 
not reached by the methods of collecting employed. 

Phyllotreta sinuata (Steph.) (Fig. 27, C) 

Leaf-beetles of the species named were taken in varying numbers 
and only in the leaf stratus during most of the study; they disappeared, 
however, for a short period during the coldest weeks. 

Meracantha contracta (Beauv.) (larva) (Fig. 27, B) 

The larvae of this tenebrionid appeared, chiefly in the leaves but 
a few in the soil, throughout most of the winter. They were more abundant 
in the early fall, when the ground strata were drier, disappeared about 
the time of the autumn rains, but were present throughout the coldest 
weather. They did not take part in the population rise during the month 
of February. This is a very characteristic influent of the leaf society, 
often appearing as a dominule in the microhabitats furnished by de- 
caying down timber (Adams, 1915). 


82 ILLINOIS BIOLOGICAL MONOGRAPHS [446 


Myodochus serripes Oliv. 

The slender-necked bug appeared on the herbs in the fall, migrating 
into the leaves and thence into the soil. While most of the specimens 
were taken in the leaf layer, this was in the fall and there is reason to 
suppose that most of these animals hibernate deeper. The species was 
taken from among the dead leaves of this habitat by Adams during the 
season of hibernation (Adams); as he remarks, and as is true for certain 
other species found here by the writer and by Weese (1924), such examples 
“show how during the hibernating season many animals are to be ex- 
pected here which at other seasons live in other habitats.” 

Cantharis sp. (larva) (Fig. 27, A) 

The larvae of this cantharid beetle were taken almost entirely from 
the leaf stratum at intervals during the whole series of collections. They 
showed their maximum increase of population during the week of Febru- 
ary 23, when so many species appeared in increased numbers. 

Fannia sp. (juvenile) (Fig. 31, G). 

The larvae of Fannia were very characteristic inhabitants of the layer 
of forest floor litter, the only stratum from which they were collected. 
They gradually decreased in numbers as the soil temperature fell, dis- 
appearing entirely from the collections during the coldest period. A few 
were taken during the middle of February; this was a period when the soil 
temperature was slowly and steadily rising. 


Predominants of the Fontaria (Top-soil) Society 


Lasius flavus Fabr. subsp. nearcticus Wheeler. 

Two small communities of this ant were captured entire on October 13 
and November 10, respectively. The same general remarks apply to them 
as to Leptothorax curvispinosus. 

Fontaria virginiensis Dru. (Fig. 31, D-c, d). 

This large myriapod is common in the humus and forest-floor litter 
of deciduous forest (Adams, 1915; Shelford, 1913). During the winter 
it appeared in the leaf litter only once in small numbers, and a few were 
taken from this stratum early in the collecting. With these exceptions, 
the species appeared only in the soil for the period of this study. The 
largest population appeared at the time of the general population increase 
during the warm weather of February, and accompanied a gradual rise 
in soil temperature. Two earlier but lower apices for this species, falling 
on December 1 and January 5, did not appear to be correlated with any 
particular changes in physical factors. They were perhaps due to the 
fortuitous selection of unusually well-populated quadrats. The species 
was not taken after the cold weather of March, until the close of the 
period of study on which the present report is based. 


447] A COMPARISON OF ANIMAL COMMUNITIES—BLAKE 83 


Pokabius bilabiatus (Wood) (Fig. 31, B-c, d). 

This centipede is reported by Weese for his ground stratum in July, 
October and late November. The writer found it in the soil stratum dur- 
ing the early part of the study, where it was a constant resident until 
it disappeared on December 8 with the lowering of the soil temperature. 
There is evidence of a stratum-to-stratum migration upwards from soil 
to leaf-litter during the week of November 10-17, followed by a return 
downward to the soil. The two warm, wet weeks of February 9 and 23 
brought numbers of these centipedes up into the leaf-litter. With the 
colder week of February 16 and the decided temperature drop of March 2, 
the curves show that the animals dropped entirely out of the leaf society, 
and were present in smaller numbers in the soil. Doubtless most of them 
had withdrawn into the deeper soil where they had spent the colder weeks 
preceding. 

Onychiurus armatus Tullberg. (Fig. 29, B) 

Spring-tails of this species occurred in some numbers in the soil stratum 
during the latter part of January and the first of February; they were 
not taken at any other time. 

Onychiurus fimetarius (L.) (Fig. 29, A). 

The maximum abundance of this spring-tail fell on March 2, prac- 
tically the only time it was taken. This was a very cold day, and the other 
species of Collembola, some present as numerical predominants during 
the preceding warm week, had disappeared. 

Ptilodactyla serricollis (Say) (Fig. 28, B) 

This beetie was collected from time to time through the entire period 
of study; it was sometimes taken from the leaf stratum as well, but was 
more common in the top-soil. 


Predominants of the Linyphia (Herb) Society (Autumnal) 

Linyphia phrygiana C. Koch. (Fig. 26, A) 

Young of the hammock-spider were collected from the shrub and herb 
strata at various times during the fall and early winter, disappearing 
with increasing cold into retreats where they were not reached by the 
collecting methods employed. A scanty appearance of the species occurred 
during the warm week of February 9. 

Lathrididae (undetermined) 

Lathridid beetles of undetermined species were fairly common on the 
shrub and later on the herb stratum in the fall and early winter; the last 
were swept from the herbs on December 8. They were not taken there- 
after nor in the lower strata. 

Tetragnatha sp. 

Young Tetragnathas were constantly taken from the herb stratum 
during the early part of the study; they disappeared on December 8, 


84 ILLINOIS BIOLOGICAL MONOGRAPHS [448 


reappearing in small numbers at herb level on February 23; they were 
not taken at any level during the intervening period. 

Epitrix brevis Sz. (Fig. 28, A-a, b, c and d). 

The results obtained for this chrysomelid support the conclusions 
of Weese on its autumnal migration and hibernation. Small numbers 
were present at shrub and herb levels on October 6, and large numbers 
on the herbs the week following. They then entirely disappeared from 
all strata until the warm week of December 8, when a few were taken 
in the leaf stratum. The species was not again taken above the soil stratum, 
and rarely there. Jvidently hibernation is deep, as Weese suggests. 


Vertebrates of the Winter Society 

Vertebrate animals, except birds, are of few varieties and not par- 
ticularly abundant in individuals in the area studied. The reason for this 
has been given by Weese; the forest was depleted of much life by a period 
of heavy grazing and consequent depletion of ground cover, and on the 
removal of this factor the isolation of the tract prevented the reestablish- 
ment of forms which had once become extinct or migrated. The forms 
which remain, however, are those characteristic of the habitat in an un- 
touched condition. 

No attempt was made to study the mammal population in detail; 
the following notes are from general observations made in various ways 
of the presence of common species, based on sight records, tracks in snow, 
partly-eaten food, etc. It will not be possible to do more than give a general 
idea of what mammals are present in this and similar habitats of the region, 
and the relative abundance of the more common species. The two most 
abundant mammals are unquestionably the white-footed mouse (Per- 
omyscus leucopus noveboracensis (Fischer) and the short-tailed shrew 
(Blarina brevicauda (Say). The writer is indebted to Dr. M. S. Johnson 
for this information, gained in extensive trapping with both box and 
guillotine-traps for the former animals, that they are much the more 
abundant of the two. There is a great gap between the numbers of these 
animals and those of the next most numerous species, the fox-squirrel 
(Sciurus niger rufiventer (Geoffroy)) and the cottontail rabbit (Sylvilagus 
floridanus mearnsii (Allen)), of which the former is probably somewhat 
the more abundant. Less common appears to be the mole (Scalopus 
aquaticus machrinus (Rafinesque)), although its work was frequently 
encountered in digging out the soil collections. These represent the 
mammals that are definitely known to inhabit the tract under considera- 
tion. Other species, characteristic of the habitat (Wood, 1910) and some 
of them known to exist at present in similar wooded tracts within a few 
miles, are: the opossum (Didelphys virginiana Kerr), the chipmunk 
(Lamias striatus lysteri (Richardson)), flying squirrel (Sciaropterus volans 


449] A COMPARISON OF ANIMAL COMMUNITIES—BLAKE 85 


(Linnaeus), red fox (Vulpes fulva Demarest)), raccoon (Procyon lotor 
(Linnaeus)), weasel (Putorius noveboracensis Emmons) and_ probably 
the long-tailed shrew (Sorex personatus I. Geoffroy-Saint-Hilaire). 

Of these animals the only ones which would be likely to directly affect 
the rest of the animal community during winter are the short-tailed shrew 
and the mole. The activities of the latter at this season of the year are 
confined to levels below those where collecting was done. The shrews, 
however, probably feed to a very considerable extent on the hibernating 
population of invertebrates in the forest-floor. 

During the period between January 5 and March 2 an attempt was 
made to take a bird census of the area under study. The area was visited 
for this purpose at least weekly and frequently oftener. An attempt 
was made to arrive at a quantitative result as well as a qualitative one; 
great conservatism was observed in making the estimates, which are 
therefore believed to be well on the side of safety. The results are given 
in Tables XXI-XXV, Table XXI gives the estimated numbers for species 
constantly present, their location in the forest and stratal occurrence. 
Table XXII gives the same information for frequent visitors, Table 
XXIII for occasional visitors, and Table XXIV for a few early migrants 
observed during the latter part of the study. Table XXV gives the list 
of species with numbers and dates when observed. 

These data will be discussed only in relation to the effect of the winter 
birds on the hibernating invertebrates. Considering the species which 
are present in any numbers it appears that there are few if any of the actual 
residents which would be expected, from our knowledge of their food 
habits, to feed or the large population of insects and other invertebrates 
in the leaf stratum. The important birds are either seed-eaters or insect- 
eaters which, like the woodpeckers, get their food from the tree stratum. 
The flicker may occasionally feed on the forest floor, for it is sometimes 
seen there, but its doing so is apparently exceptional. It does not seem 
likely that the birds listed, either from their numbers or their food 
habits, can produce much effect on even the animals of the leaf stratum, 
and we know that many species hibernate out of reach entirely. 


DISCUSSION AND SUMMARY 


The present study began before the close of the autumn migration 
of animals from the forest border and from the herbs and shrubs of the 
forest itself into the leaf layer for hibernation. This migration had well 
progressed before the temperatures had become extremely low, but was 
no doubt incited by their gradual decline during the first part of the period 
of study. As far as this migration concerns forest border species, those 
migrate inward on their own strata and then downward to the forest 


86 ILLINOIS BIOLOGICAL MONOGRAPHS [450 


leaf-layer; this was determined by Weese for a number of beetles and 
the writer obtained evidence in the same direction for some other species. 
The downward migration may be delayed on the herb level, in the leaf 
level or in the upper soil, or the animals may disappear at once from 
the shrub level into deeper hibernation. As far as the forest-border insects 
are concerned, the movement towards winter quarters seems to be corre- 
lated with temperature changes, to be continued rapidly on falling temper- 
atures and arrested more or less on rising ones. 

Other animals, living earlier in the season in the upper strata of the 
forest itself, migrate downward at the same time. They behave in a 
very similar way as far as the effects of temperatures are concerned, 
entering the leaf stratum more promptly with falling temperatures. 
The evidence indicates that different species react differently to the 
factors inducing hibernation, and that the reactions for a given species 
are constant from week to week and from year to year. Certain forms mi- 
grate at once to the deeper strata and are not seen again until the time 
of emergence in the spring. Other species remain comparatively near 
the surface, in the top-soil or leaf strata or both, and seem to fluctuate 
in abundance in activity with the changing conditions. Ordinarily these 
animals are the ones which determine the fluctuations in numbers found 
in samples. 

Extreme changes in either direction may cause marked differences 
not only in the size but also in the composition of the samples. Extreme 
cold in the soil layer reduces the population to some extent, but less 
than might be supposed; temperatures rising to the thawing point, es- 
pecially if accompanied with abundant moisture, bring up a large pop- 
ulation, composed in part of hibernating animals from various strata 
but mostly consisting of the moisture-requiring permanent residents 
of the forest-floor. On the other hand, cold or dryness in the forest-floor 
markedly reduces the numbers of the resident enchytraeids, mollusks 
and spring-tails. That certain species are much more sensitive than 
others is indicated by the very different seasonal distribution of vari- 
ous species of Collembola and mollusks throughout the period of 
study. 

The changes in temperature, as shown by the curves, are much more 
gradual in the forest floor than in the air above it. Indeed, it is evident 
that the decline does not trap any great numbers of animals in the frozen 
upper layers, and does not seem to affect adversely most of the animals 
which do remain there during freezing. The invertebrate population 
of the upper ground strata, once the freezing point is approached, seems 
to consist of species which are able to tolerate complete freezing with 
little harm, but before this condition is reached many animals migrate 
downward. On the other hand, very warm periods call up from deeper 


451] A COMPARISON OF ANIMAL COMMUNITIES—BLAKE 87 


hibernation species never found during winter weather; on the return 
of the cold, these forms soon disappear, returning to the regions lower in 
the ground, probably below the frost-line. 

The different reactions of various species to changing conditions 
of the physical environment is of great interest. We must assume that 
the winter is a period when biotic influences are at their lowest, and 
the maximum role is played by physical factors. To this extent the chang- 
ing earth temperatures may be looked on as a series of natural experi- 
ments on the effect of changing the physical environment. The animal 
responses thus evoked appear distinct for various species of the same 
group. Thus certain species of Collembola, mollusks, etc., present at 
one period in distinctly predominant numbers, during other periods 
disappear wholly or in part and are replaced by other species from these 
same groups. These differences in predominants can hardly be considered 
societies, in the sense of the use of that term by plant ecologists. They are 
too brief, and their disappearance is probably caused merely by local with- 
drawal to deeper areas. They represent the response of some species to a 
particular complex of physical factors to which other species of the same 
group are negative or neutral. Such responses may be as definite specific 
characters as morphological ones. 

It is an ecological axiom that animals react most accurately to phys- 
ical changes of kinds affecting them under natural conditions. The in- 
vertebrate population of winter forest is a stratal population occupy- 
ing, generally speaking, only the leaf and soil strata. We should expect 
to find its members responsive to changes within those strata, and to 
a large degree this proves true. Thus the curve of population only roughly 
coincides with the curve of air temperature, and this largely because 
the leaf stratum, in contact with the atmosphere, has its temperature 
more or less directly affected thereby. So far as could be observed there 
existed no correlation between animal population and atmospheric humid- 
ity; the changes in this factor are little indicative, in winter, of condi- 
tions in the soil and leaf strata. But soil and leaf moisture, though it 
was not measured and could not be separated in its effects from tempera- 
ture, appears to be a factor of importance. 

It has been said that biotic influences were at their lowest among 
the hibernating population of forest floor invertebrates. Most of the 
animals were in a quiescent or dormant condition when collected, al- 
though they soon revived when exposed to warmth. There was no ev- 
idence of activity among spiders, nabids or other predatory species, 
and on even the days when conditions were such that some animals 
were seen among the dead herbs and leafless shrubs, they were rather 
torpid. As has been seen, the effects of the activity of vertebrates on 
the forest floor animals are probably negligible. 


88 ILLINOIS BIOLOGICAL MONOGRAPHS [452 


CONCLUSIONS 


Temperature is the climatic factor which seems to be of greatest 
importance to the winter forest population; this factor is well stratified, 
the higher strata showing greater extremes and lower mean temperatures. 
The stratum whose temperature is of importance to hibernating animals 
is the ground; here is the highest and most uniform of the three stratal 
temperatures studied. Atmospheric temperature is of importance only 
in so far as it affects the ground, and especially its leaf stratum. 

There is no evidence that atmospheric humidity shows any direct 
correlation with the population of hibernating animals. 

Moisture present in the forest floor appears to be a factor in the weekly 
variations in the numbers of animals in the samples. An increase of 
moisture in winter, however, is almost always accompanied by a rise 
in temperature, and the separate effects can only be inferred. 

Biotic factors seem to play little or no part in the weekly fluctuation 
in numbers. Invertebrate predators are themselves quiescent at this 
time. The vertebrates feeding on the forest floor insects are not present 
in sufficient numbers in winter to have any marked effect. 

The first response of animals to the falling temperatures is the descent 
of shrub animals to the herb level; this is characteristic both of inwardly 
migrating forest-border species, such as certain beetles, and of true forest 
shrub animals, such as many young spiders. From the herb stratum 
the animals pass downward into the leaves. 

Some animals remain in the leaves for the entire winter; others until 
this layer becomes colder; others make only a brief stop; while the re- 
mainder pass directly into the soil beneath. Behavior in this regard 
appears to be a species characteristic. The members of the last group 
do not reappear, as a rule, during the winter. 

The animal population fluctuates somewhat between the leaf and 
upper soil strata but less than would be expected. Conditions sufficiently 
severe to markedly reduce the number of individuals in the leaf usually 
drive the animals deeper into the earth than the upper 10 cm of soil. 
The reverse is also true; conditions which cause any noticeable increase in 
the leaf population do so by affecting the soil deeper than the top layer. 

Many resident animals of the forest-floor show very marked response 
to changing physical factors—especially temperature and moisture—by 
migrating vertically. Such animals as spring-tails, Mollusks and en- 
chytraeid worms are the numerical dominants of the forest-floor strata 
in winter, and probably at other times as well. From their huge numbers 
and constant presence some of these animals may be considered as pre- 
dominants of these stratal socies. 

After the fall migration downward, the herb and shrub socies are 
insignificant in their contributions to the general population. The soil, 


453] A COMPARISON OF ANIMAL COMMUNITIES—BLAKE 89 


in its upper 10 cm., gives a rather uniform but low animal count. The 
leaf stratum varies enormously and determines, by its curve, the curve 
of the total population. 

The animals in the leaves and upper 10 cm of earth are uniformly 
found in a condition of dormancy from cold. They are frequently frozen 
solidly into the earth and leaves for weeks at a time. There is no evidence 
from the present study that this exposure to low temperatures is injurious 
to them, as they become active when thawed out. 

The large number of animals often recorded for a single week is partly 
due to the presence of one or more species which appeared exclusively 
at that time. This seems to indicate a capacity for response quite different 
among different species in the same group. It suggests, in addition to 
the recognized, morphological differentiation, physiological distinctions 
between species. The data at hand relative to the winter populations, 
etc., will be compared with that of Weese and others later. 


90 ILLINOIS BIOLOGICAL MONOGRAPHS [454 


GENERAL DISCUSSION AND SUMMARY 


The process of biotic succession tends constantly to cover bare areas 
of the earth’s surface with a climax biota of vegetation and its animal 
inhabitants; this climax is determined primarily by climate (Clements, 
1920). Animal succession over such areas is correlated with—and to a 
large extent determined by—plant succession. Under favorable conditions 
the climax may develop swiftly, its dominants becoming well established 
in a comparatively few years (McDougall, 1918). Under greater stress 
of unfavorable climate and soil the subclimax stages may be of very 
long duration; the montane tundra studied in the first part of this survey 
is a preclimax stage of coniferous forest showing arrested development 
(Harvey, 1903). 

The vegetation climax in all the areas under consideration is forest; 
for the first. and second studies it was northern coniferous forest (northern 
mesophytic evergreen of forest of Shreve and Livingston, 1921) and for 
the second it was deciduous forest (McDougall, 1922). The general 
succession of biota following the last glacial retreat is pictured by the 
present day distribution of biotic types from the Arctic Ocean south- 
ward; that is to say, tundra, coniferous forest and deciduous forest, 
in the order named (Adams, 1905). We are therefore justified in consider- 
ing that a study of these stages should give some idea of the process 
of animal succession accompanying the slow northward migration of 
climaxes at the close of glaciation. If we substitute for the subarctic 
low tundra the alpine high tundra of the northern Appalachians, we still 
have a comparable series, since a large proportion of the characteristic 
species is common to both. 

Beginning with bare rock areas, which we may assume not to differ 
essentially as biotic habitats from similar areas left by the retiring ice- 
sheet, we find thereon a scanty covering of lithophytic plants, independent 
of animals. The animals present are principally small lichen-feeders 
and lycosid spiders belonging to species characteristic of this habitat 
in high and low tundra regions. Climatic conditions are extremely severe, 
temperatures ranging as much as 28°C. between sun and shade and 
wind velocities approximating 110 miles per hour. In the absence of 
any appreciable plant cover, these must exert a maximum effect on 
animal life. The dominant animals live in openings among and under 
the rocks, and their habits are adjusted to this type of life; the community 
thus consists of one stratum only. Succession from this stage waits on 
the formation of a soil, in which process both biotic and physical factors 


455] A COMPARISON OF ANIMAL COMMUNITIES—BLAKE 91 


are involved. There is evidence that the latter are of particular importance 
in these early stages, although the former cannot be ignored. 

With the formation of finer rock fragments and the retention among 
them of a coarse granitic soil, to which the pioneer biota contribute 
a sparse organic component, we have the establishment of the early tundra, 
a shallow sod overlying rock and hence comparable to arctic low tundra, 
which overlies continually-frozen soil. On this sod and largely composing 
it are characteristic plants, among which grasses and sedges are most 
conspicuous. The whole furnished the home for an animal associes of 
of different species and life histories from those inhabiting the rock area, 
The plants furnish a more abundant food supply and the dominant 
animals are species of Cicadellidae which are characteristic of such host- 
plants. Climatic stress is still as severe as on the rocks, but the soil and 
alpine grasses furnish a partial shelter during the frequent storms and 
low temperatures of the short summer, as well as a means of retaining 
moisture and heat. During the winter the thin cover of earth and dead 
herbage furnishes a place for hibernation; that it is efficient shelter is 
indicated by the numerous and varied population which appears in the 
late spring on the high tundra, as well as by studies made on animals 
hibernating in the frozen upper layer of earth in other habitats. 

This associes has really two socies, soil and herb, but the animal 
population seems to leave the shallow soil almost ex masse during the 
warm period of the year. Thence on, the process of succession is increas- 
ingly dependent on the biotic factors; the climatic factors, local or regional, 
are retarding in their effects. With the increase in depth and organic 
matter in the soil, the latter amounting to 34.5%, a succession to the 
last stage of tundra community is attained. The capacity for moisture 
and heat retention becomes greater as the soil and vegetation cover 
increase in thickness, and hibernation probably takes place under some- 
what more favorable conditions. Further succession on the plant side 
is characterized by the heaths. The animal community is different from 
that of the early tundra, the differences, however, being chiefly caused 
by the appearance of phytophaga, especially cicadellids and aphids, 
associated with the plant dominants, while the grass-eating forms of 
the early tundra disappear. Although species have changed, there seems 
no reason to expect a marked change of mores, nor is there any evidence 
of such a change. The dominant animals are still such as are character- 
ized by short summer activity and long hibernation periods. The heaths 
are so low as to be of no more than herb proportions, and stratification 
of the animals remains unchanged. At this stage of succession, in addition 
to the various associes of invertebrates, some of the vertebrates of the 
climax forest appear, either as visitors or as more or less permanent 
residents; especially is this true of small mammals. 


92 ILLINOIS BIOLOGICAL MONOGRAPHS [456 


With the establishment of the heaths, the tundra series comes to 
an end. On the increasingly deep soil, due to the deposition of organic 
material by successive generations of plants and animals, the forest 
is able to become established, bringing with it forest conditions and 
forest animals. Here, however, the local climatic factor of wind makes 
itself felt, and the first forest to gain a footing is the krummbholz or elfin- 
wood. On the advent of its low-growing but dense thickets the habitat 
changes. Evaporation is reduced, the terrific velocity of air-movement 
felt in the open becomes much lessened, and temperatures are much 
more uniform. Perhaps as important as any of these, the new habitat 
furnishes an abundance of materials for abode. The conditions required 
for distinct stratification into animal societies become present for the first 
time, and stratification of the biota is important in all later stages. In 
the krummholz it is shown especially well by spiders. 

The development of the krummbholz into climax coniferous forest 
is not accompanied by any very marked changes in the whole biotic 
association, although stratification becomes more marked, and there 
is a large increase in the number of animal species. It is possible that 
this is due in part to the removal of the conditions of climatic stress which 
are connected with krummholz formation, but there is no direct evidence 
that this is so. Rather is it due to the more varied nature of the coniferous 
forest habitat at lower levels, and its interruption by local habitats, 
such as bog, meadow, streamside, slash and forest-margin communities. 
In other words, the animal communities of the climax forest, as compared 
with those of the krummholz, seem more closely correlated with the 
massed biotic conditions than any particular physical factors. 

Coniferous forest presents a well-stratified habitat, where conditions 
are much more uniform, for any given period of the year, than those 
found in any of the preclimax stages. This uniformity is caused in part 
by the absence of the alpine conditions which have held tundra and 
krummholz in a subclimax state, and in part by the influence of the forest 
cover itself. Its most marked physical feature is the constancy and sharp- 
ness of the various strata; this is in turn correlated with, and principally 
caused by, the stratification of plant societies. It is accompanied by a 
stratification equally sharp, as far as it has been observed, for the animal 
societies. 

Beginning in the forest floor we have in the soil a level of relatively 
constant temperature, whose summer mean is 14°C, with a mean range 
of only 2.3°C. Moisture is usually high and light scanty. We must 
assume that all these factors are present in higher percentage than in 
the shallow tundra soil. This stratum has a small but rather constant 
summer population; its winter population has not been studied, but 
it must be increased by immigrants for hibernation. The predominant 


457] A COMPARISON OF ANIMAL COMMUNITIES—BLAKE 93 


animals are those characterized by a considerable moisture requirement, 
tolerance of fairly low summer temperatures and a preference for dark- 
ness; the ground-dwelling larvae of Elater will serve as an example. 

Next above this is the leaf stratum, largely composed of dead co- 
niferous needles. Its physical conditions are somewhat different from those 
of the soil stratum. Temperature averages about 1°C higher than in 
the upper portion of the soil stratum, but moisture is still abundant; 
daily evaporation is only .08 cc from the lower part of the leaves. The 
characteristic animals have a greater capacity for adjustment to changing 
conditions than the soil animals possess, as evidenced by the fact that 
they may occur in leaf, soil or, more rarely, on the herbs. A predominent 
animal in this stratum is the spring-tail Tomocerus flavescens. Leaf and 
soil strata together form a ground society or super-society; physically this 
is indicated by the fact that the differences between them, while constant, 
are of moderate amount; biotically it is indicated by the fact that some 
animals habitually divide their time between these two strata, as temper- 
ature and moisture vary. 

In the herb stratum there is another and more marked increase in 
temperature, with a mean temperature of 17.1°C and a mean range 
of 7°C. Evaporation also rises sharply, reaching 8.2 cc.at herb level. 
Differences of the same character exist between the herb and shrub 
and shrub and high bush strata, which have a mean daily evaporation 
of 11.2 ccand 14 cc respectively; there are smaller differences here, it will be 
observed, than that existing between leaf and herb strata. Forest temper- 
atures in summer thus increase upwards in amount and range, and the 
same is true for evaporation and light. The animals of the high bush 
stratum have not been studied. The stratal occurrence of the animals 
of the next three strata below is what we should expect if it were due 
in part at least to physical factors. Thus, a rather large number of species 
habitually pass between herbs and shrubs and vice versa, while a much 
smaller number divide their time between the leaf and herb strata. This 
is of course under summer conditions, and refers to animals which during 
a given stage of their life cycle habitually divide their activities between 
the strata in question. This is apparently a temperature response in 
some cases, such as the downward migration of Clastopera obiusa and 
its return to the shrubs with rising temperatures. The tendency is seen 
to be for animals to make the traverse only between strata which are 
separated by moderate gradients. 

Above the high bushes, the coniferous forest may possess a layer of 
low deciduous trees, and above them lies the forest crown itself. The ani- 
mal population has not been studied. The instrumental observations 
indicate changes in the same physical factors and in the same direction, 
as those already mentioned. The sharp gradient falls between the high 


94 ILLINOIS BIOLOGICAL MONOGRAPHS [458 


bush and low tree strata, with a mean daily evaporation of 14 cc and 19.7 
cc respectively. is 

The hythergraphs indicate that coniferous forest of the climax type, 
as distinguished from the subclimax stages of its northern or upper mon- 
tane border, is in general a region of less climatic severity. The’ effects of 
climatic factors are modified by the forest cover of climax trees and sub- 
stratal plant societies. During the spring, summer and fall the animal 
population falls into stratal societies, which are in agreement with the 
stratification of physical factors and vegetation. ‘The latter seems to 
be of obvious importance to the phytophaga, but since even they re- 
spond to physical factors by stratum-to-stratum migrations, and since 
stratification occurs among such animals as spiders, which possess no direct 
relations with the vegetation, it seems probable that the physical factors 
are extremely important and perhaps decisive. During the winter the 
invertebrate life and to some extent the vertebrate life of this forest be- 
comes concentrated in the ground strata, and the community reverts 
for the time being to a one-stratum society, like the tundra community 
of its early successional history. 

The climax of the entire series which we are discussing is deciduous 
forest, wherever climatic conditions permit this to replace the conifers. 
The area where such succession can take place is one of higher mean 
temperatures than the region of climax coniferous forest. Deciduous 
forest of elm and maple, as studied by Weese (1924) under summer con- 
ditions seems to possess a stratification of measurable physical factors 
which agrees in all important respects with that found for the coniferous 
forest, although mean temperatures are distinctly higher throughout the 
year, the difference being approximately 5°C. 

The difference between shrub and herb temperature as contrasted 
for coniferous and deciduous forest is under 1.5°C, and evaporation 
from atmometers at the same height and exposure in the two habitats 
gives even closer comparisons: 


Mean daily evaporation in cc 
Coniferous forest Deciduous forest 


On ground under vegetation 8.2 7.3 
1 m above ground 11.2 11.2 
2.5 m above ground 14. 12.4 


It will be seen that differences are small or lacking. The whole suggests 

a general and stratal similarity of the physical factors in the two habi- 

tats. It must be remembered that the evaporating power of air is an 

index of many other physical factors, such as temperature, humidity 
and air movement. 

The stratal societies of animals described by Weese for elm-maple 

forest appear in decided harmony ecologically with such societies observed 


459] A COMPARISON OF ANIMAL COMMUNITIES—BLAKE 95 


by the writer for coniferous forest. This may be illustrated by comparing 
lists of equivalent predominants from the summer shrub societies of 
the two habitats: 


Coniferous forest Deciduous forest 
Clastoptera obtusa Emt .asca viridesces 
Tetragatha sp. Tetragatha laboriosa 
Graphocephala coccinea Evythroneura obliqua 
Philodromus sp. Xysticus elegas 

Diaphidia pellucida Epitrix brevis 


It will be seen that while there is no positive identity of species (the 
writer‘s Tetragnathas were too young for determination to species) 
there is a decided ecological similarity between the respective dominants, 
some of which belong to the same family. Even where the animals are 
widely separated taxonomically, as in the case of Diaphnidia pellucida 
and Epitrix brevis, their similar habits, life-histories and relations to 
the community, justify their consideration as ecologically similar. There 
are thus no greater differences between the animals of corresponding 
strata, or between the mores of the prominent species, than might be 
expected to occur between different associations of the same formation, 
altnough most of the species are different. 

Certain widely ranging species occur in both habitats; examples 
are Phylomycus carolinensis, Hahnia agilis, Linyphia phrygiana, Ther- 
idion frondeum, Gypona 8-lineata, Scaphoideus autontinens, Camponotus 
herculeanus pennsylvanicus, Formica fusca and Myrmica_ scabrinoidis 
schenoki. Their presence in corresponding strata of both coniferous 
and deciduous forest indicates that to such animals the local conditions 
of the biotic association are of major importance; the general climatic 
conditions of less importance, or none at all within the ranges considered. 

The various animal societies in both coniferous and deciduous forest 
are thus seen to be composed of animals with similar mores, of whatever 
species, or to phrase it differently, both habitats possess stratal socies 
composed of animals which are ecologically equivalent. These animals 
respond in a similar way to the measured stratification of physical factors 
and to their fluctuations, as well as to the observed stratification of plants. 
There is some evidence that the comparison between the two habitats 
is as close for seasonal societies as for stratal ones, but coniferous forest 
was not studied for this at critical periods. What evidence exists tends 
in this direction. 

It hence appears that ecologically it is the forest cover, that is, the 
biotic association as a whole, that is of importance in determining these 
two animal communities. The nature of the cover, which is in turn de- 
pendent on the climate, is a secondary consideration. Stratification of 


96 ILLINOIS BIOLOGICAL MONOGRAPHS [460 


animal communities is thus seen to be fully developed in the preclimax 
forest, as soon as the forest cover becomes well established. So far as 
we have evidence, it agrees in all important particulars with the same 
phenomenon in climax deciduous forest. The cover of tall trees, with 
substrata of lower vegetation at different levels, appears to be the deter- 
mining factor for the presence of a typical forest animal community. 
The nature of the trees, the character (within the limits discussed) of 
the climate, are of less value. Given such a biotic complex has been de- 
scribed, it becomes inhabited by a statified animal community during 
the warmer portion of the year. 

With the advent of autumn in both forest habitats, there is a general 
change of the distribution of population. Urged by factors which are not 
fully known, but among which temperature is probably of prime im- 
portance, there begins a downward migration of the animals of the upper 
strata. This may be preceded or accompanied by an inward migration 
of forest-margin species (Weese). The entire phenomenon has already 
been discussed, and it will only be said here that it results in the reduction 
of the forest community, during the winter, to the status of leaf-soil 
society. What animal activities exist are confined to vertical migrations 
in the forest-floor, correlated with temperature and moisture fluctuations. 
In the coniferous forest habitat the cold is usually so sustained and the 
covering of snow so deep and enduring, that it is doubtful whether 
any important vertical movements take place. Under the milder con- 
ditions prevailing in the deciduous forest formation snow often does 
not lie through the entire winter, and warm rains may entirely thaw 
and wet the leaf and soil strata from time to time. Here vertical mi- 
grations may assume large proportions, such a warm and rainy period 
increasing the population of a two-foot quadrat by hundreds of percent. 
The amount and character of such response seems to be in some cases 
a species characteristic; thus among several species of collembola and 
mollusks, certain ones appear definitely for one period and set of con- 
ditions, other species at other times and under different conditions. 
This phenomenon has not, however, received any detailed study. 

Many animals pass the winter in the leaf and top-soil strata, where 
they are solidly frozen in during considerable periods. The present study 
afforded no evidence of particular mortality among the animals so ex- 
posed. 

Winter is thus a period when the forest loses its stratification of animals 
(birds, some mammals and some tree-inhabiting insects excepted). It 
is a period when the greatest climatic effect is shown in the restriction 
of the activities of the community and when, as has been shown, biotic 
interrelationships are of least importance. It might be said that there 
exists here an analogy between the forest floor in winter and the early 


461] A COMPARISON OF ANIMAL COMMUNITIES—BLAKE 97 


tundra; both are single-stratum communities where climatic effects 
are marked and restrictive and biotic effects of comparatively low value. 

Further studies in the whole community cycle of forest and tundra 
communities, especially in their response to the annual rhythm, would 
no doubt throw much light on the problems of ecological distribution. 
It seems evident that the relations between such distribution and measur- 
able physical factors are less simple than has been supposed, nor do studies 
of physical factors made in different habitats at the noncritical period 
of the year yield, in themselves, data which will explain why certain 
animal communities are found there. Studies of the entire biotic com- 
plex of a given habitat involving the collection of quantitative as well 
as qualitative data on animal populations, are needed and if possible 
such studies should be carried through one or more annual cycles in the 
same habitat and locality. It is suggested that alpine conditions, though 
they present special problems, might furnish a valuable field for such 
investigation; there the entire period of activity is condensed into a few 
months, during which all the seasonal societies could be studied, from 
the time of emergence to that of hibernation. 


98 ILLINOIS BIOLOGICAL MONOGRAPHS [462 


CONCLUSIONS 


Alpine tundra animal communities in the northern Appalachians, 
as contrasted with those at higher altitudes, show succession of pre- 
dominants and mores from associes inhabiting bare rock to those char- 
acteristic of northern coniferous forest. 

The animal communities of coniferous and deciduous forests have 
a different taxonomic composition; only 4.5%, all non-predominants, 
are common to both. Stratal societies are ecologically similar in the two 
habitats; thus a shrub predominant of coniferous forest, such as the 
cicadellid Graphocephala coccinea, is represented in deciduous forest 
by species, such as Erythroneura obliqua, possessing a similar type of 
life history. The same is true for the other strata. 

The climatic difference between the two habitats are sufficiently 
marked to affect the biota; the deciduous forest, at 44°N. lat., possesses 
a mean temperature higher by 4.1°C and a relative humidity lower 
by 5.5% than those found in the coniferous forest, at 45°N lat. 

The physical differences between corresponding strata of coniferous 
and deciduous forest are insignificant; the evaporating power of air 
at the same height and exposure is approximately the same for both. 

The stratal societies within these two communities are correlated 
with physical and biotic differences at different levels; their vertical 
distribution is independent, within the limits considered, of the climatic 
conditions determining the association as a whole. 

Hibernating animals in deciduous forest show by vertical migra- 
tions a stratal response to changes in physical conditions; there is no 
evidence of excessive mortality during hibernation. 

Negative evidence in regard to the physical conditions in the co- 
niferous and deciduous forest habitats indicates the importance of in- 
vestigating life cycles of both species and communities in their relation 
to annual rhythms, as the most promising method of attacking the prob- 
lems of ecological distribution. 


463] A COMPARISON OF ANIMAL COMMUNITIES—BLAKE 99 


ACKNOWLEDGEMENTS 


The author’s thanks are particularly due to Professor V. E. Shelford, 
under whose direction the work was done and whose assistance and sugges- 
tions have been invalubale. The list of those to whom the writer is in- 
debted for the determination of material is very long one. To Dr. T. H. 
Frison of the Illinois Natural History Survey, thanks are due for the 
identification of Bremidae and for assistance of inestimable value with 
insects in general. Mr. J. H. Emerton named the spiders, and generously 
sent many notes on life histories and occurrence. The writer wishes 
to express his thanks to Mr. C. A. Frost who, at a critical period of the 
study, determined a large collection of Coleoptera on very short notice. 
In addition to the specialists already named, very valuable assistance 
was rendered by the following in identifying material belonging to special 
groups: J. B. Christie and C. Steiner (Mermithidae), Frank Smith (Lum- 
bricidae), F. C. Baker (Mollusca), J. O. Maloney (Crustacea), C. R. 
Crosby (Phalangida), H. E. Ewing (Acarina), J. W. Bailey (Myriapods), 
J. W. Folsom (Collembola), A. P. Morse (Orthoptera), Nathan Banks 
(Neuroptera and Corrodentia), J. G. Needham (aquatic insects), W. R. 
McAtee (Hemiptera), H. B. Hungerford (Corixidae), C. J. Drake (Ger- 
ridae), H. H. Knight (Miridae), H. M. Harris (Nabidae), H. G. Barber 
(Lygaeidae), Herbert Osborn (Homoptera), D. M. DeLong (Cicadellidae), 
E. M. Patch (Aphididae), P. W. Mason (Aphididae), H. C. Fall (Coleop- 
tera), A. G. Boving (coleopterous larvae), W. C. Woods (aquatic Chrys- 
omelidae), C. K. Sibley (Trichoptera), W. T. M. Forbes (Lepidoptera), 
F. H. Benjamin (Lepidoptera), August Busck (Lepidoptera), H. G. Dyar 
(Lepidoptera), Carl Heinrich (lepidopterous larvae), C. W. Johnson 
(Diptera), C. P. Alexander (Tipulidae), J. M. Aldrich (dipterous larvae), 
S. A. Rohwer (Hymenoptera), A. B. Gahan (Hymenoptera), R. A. Cush- 
man (Ichneumonidae), M. R. Smith (Formicidae), W. M. Mann (Formi- 
cidae), G. S. Miller, Jr. (mammals). Dr. A. O. Weese kindly submitted 
identified material from the area worked by him, and Mr. A. H. Norton 
has permitted citations from unpublished data on the birds of Mount 
Ktaadn. The writer also wishes to extend his thanks to Dr. L. H. Merrill 
and Professor H. W. Smith of the University of Maine for soil analyses; 
to President C. C. Little and Dean J. S. Stevens for the loan of instru- 
ments; and to Mr. D. B. Demeritt for an instrumental survey of one 
of the areas studied. 


100 ILLINOIS BIOLOGICAL MONOGRAPHS [464 


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104 ILLINOIS BIOLOGICAL MONOGRAPHS [468 


TableI 
Soil Data 
Soil samples from Mt. Ktaadn. 
Organic 
and Organ- CGe 
volatile ic and = n/100 Clay Sand 
Station Water Dry mat- sub- Ash _ Vola- Ba(OH), Depth and % 
% ter,% stances % tile N per of silt 
in dry % 10 gms. sam- % 
matter, ple 
% 
Alpine 28.22 71.78 28.37 43.41 0.49 1.5 Sin. 36.4 63.6 
Tundra 
(Grass) 
Alpine 
Tundra 18.36 81.64 61.70 19.94 0.76 0.6 8 in. 22-3 77.7 
(Heath) 
Krumm- 


holz 21.14 78.86 58.48 20.38 0.38 1.8 1 ft. 41.0 59.0 


100 parts dry matter contain 


Organic and Ash Nitrogen in organic Depth of 
Volatile matter sample 

Alpine 
Tundra 39.6 60.4 1.70 8 in. 
(Grass) 

Alpine 
Tundra 71555 24.5 1.23 8 “ 
(Heath) 

Krumm- 

holz 74.1 24.9 0.65 12 


Quantity of water in relation to dry matter is probably not significant, for although 
the samples were kept in tightly corked bottles until analyses could be made, a considerable 
time elapsed before this could be done. 


Table II 
Biotic Data 
Mammals Recorded from the Upper Stations of Mount Ktaadn 


Common Name Scientific Name Author 
Red Squirrel.............Scturus hudsonicus loquax Bangs*.............- B.H.D. 
White-footed Mouse...... Peromyscus maniculatus abietorum (Bangs)... ... 
Porcupine...............Evrethizon dorsatum dorsatum(Linnaeus) esis eae 
(Bog-lemming)..........Synaptomys sphagnicola Preble...............- Bei Ds 
Short-tailed Shrew. ...... Blarina brevicauda talpoides (Gapper)........--- 


Red'Poxs.c.2eccsnaunes Vulpes fulua (Demarest)..........-.........--R.D. 


469] A COMPARISON OF ANIMAL COMMUNITIES—BLAKE 
Canada Lynx...........- Lynx canadensis canadensis Kerr............6- Pros 
Red-backed Mouse. ..... . Evotomys gapperi gapperi (Vigors)...........+-- 
Wroodchucke disc. rye Marmota monax monax (Linnaeus)...........-- RED: 
Varying Hare............Lepus americanus virginianus (Harlan).......... B:H..D. 
Caribou: cere. cess cree oss Rangifer caribou caribou (Gmelin)............-- B.H.D. 
SHrewisicte io eeinin tierce nes stots Sorex personatus personatus I. Geoffroy..........B.H.D. 
Weasel ii: sieecrereccirea en Mustela cicognanti Bonaparte...............05- B.H.D. 


105 


The species are listed roughly in order of their occurrence through the succession stages, 
the animals noted first being those found in the earlier associes. Many of them range through 
a number of successional stages indifferently. The species given in parentheses is the only 
one that is not found also on the lower slopes covered with Picea-Abies forest (Stations E-2, E). 


The authorities given for some of the records are: 


B.H.D. = B.H. Dutcher, “Mammals of Mt. Ktaadn, Maine” 1903 
Pus; = Percival Sayward, “A Winter Ascent of Mt. Ktaadn,” 1915 
R.D. = Mr. Roy Dudley, who was Dutcher’s guide. 


* The single specimen collected by the writer was referred by Mr. Gerrit S. Miller, 


Jr., to Sciurus hudsonicus gymnicus Bangs. 


Table III 
Biotic Data 
Mammals Recorded Only From the Lower Station of Mount Ktaadn. 


Common Name Scientific Name - 
Water, Shrew... 6. sacs: Neosorex albibarbis Cope......-2eeeceereeeces ‘a 
Marteniiccias cncce etc ane Martes americana americana (Turton).......... - 
Mink, a fireisvenaeisisvaucysys e'ciers Mustela vison vison Schreber.............-.5-- is 
Meadow-mouse.......... Microtus pennsylvanicus pennsylvanicus (Ord.)...  * 
Jumping-mouse.......... Zapus hudsonius hudsonius (Zimmerman)........ * 
Jumping-mouse.......... Napaeozapus insignis insignis (Miller).......... 
White-tailed Deer........ Odocoileus virginianus borealis (Miller).......... 
IBlack*Beareyee ciste.ciscc nce Euarctos americanus americanus (Pallas)........ a 
Pisheris csc cece eases Martes pennanti pennanti (Erxleben)........... *~ 
WiGOSe tinea te eeayciewe ae Alces americana americana (Clinton)........... 


The first part of the list contains species which have been recorded from the upper as 
well as the lower regions of the Picea-Abies taiga, especially from Chimney Pond (2,900 
feet elevation) and thence up to the foot of the steep slopes; the latter part of the list con- 
tains species listed only for the lower slopes of the mountain. None of these animals have 


been reported from the upper plateau regions. 
Mostly (records marked *) on the authority of Dutcher. 


Table IV 
Biotic Data 
Birds Recorded from the Upper Stations of Mount Ktaadn 


Common Name Scientific Name Authority 
Rutied'Grouse ica isiieteietes Bonasaumbellus... 01.0.0 sevens R.D. 
Sharp-shinned Hawk.. ......Accipiter velow.........0cce eee 
Broad-winged Hawk.......... Buteo platypterus (?)......0.-0-8- 

Bala cle nscy. cs. saceratyadcteers sys Haliaetus leucocephalus (?)....... A.H.N. 
(Crossbill): cScxcnk Hee cenncess Loxia curvirostra minor (?)....... A.H.N. 
White-throated Sparrow.......Zonotrichiaalbacollis............ 
Slate-colored Junco........... Junco hyemalis......sseccseeess 


(American pipit)................-Amthus rubescens.. 1.0... 00005- A.H.N. 


. 


106 ILLINOIS BIOLOGICAL MONOGRAPHS [470 


The species in parentheses are the only ones that have not also been recorded for the 
lower slopes covered with Picea-Abies forest. 

The authorities for records not taken by the writer’s party are: Mr. Arthur H. Norton, 
of the Portland Society of Natural History (A. H. N.), and Roy Dudley (R. D.), who was 
Dutcher’s guide in 1902. 


Table V 
Biotic Data 
Birds Recorded Only From the Lower Stations of Mount Ktaadn 


oa Common Name Scientific Name * 
@anadatGrouseyeseciveree easels ale tate Canachites canadensis canace........ 
Red-shouldered Hawk............... Buteo lineatus lineatus............44. 
Hairy Woodpeckers)... iiss cine os tes Dryobates villosus.......0+0ceceeeeee 
Downy Woodpecker.............+.5. Dryobates pubeSCems.......00cceveeee 
Arctic Three-toed Woodpecker....... PUCOULESIATCLLCUS: acs xinicoresela) sieves erates as 
American “ Bs alial este Picoides americanus. ........-2-000 
Northern Flicker... 0)... se06 6<0e0c00 Colaptes auratus luteus........00008- = 
Olive-sided Flycatcher............... Nuttalornis borealis..........-.++045 
BIG] aY: = aisssarcic.c’s a aveiees clove cise duecerste rs Cyanocilia cristatd.....006cseece sees 
Canada Jays cic ssa mocals cis wo see Peresoreus CANQdENSIS...... eee ee ees 
American: Crowe...acessres tere qeresteere Corvus brachyrhynchos.........0+000- 
PurpleP inch? science setew.ate ee Carpodacus purpureus........0000005 bs 
Cedar Waxwing sccie cccs loser ci speeeeitees Bombycilla cedrorum.........++000% 
Black-and-white Warbler............ Muiotilia varia... 0... cc cece wees be 
Myrtle Warbler? so sis.ccisiscdeettienciesea © Dendroica coronata.........-+0.000% 
Magnolia Warbler.................. Dendroica magnolia. .......0.-0000 
Black-poll Warbler.......5 65 o:cciicee see Dendroted striata. 2 siocces solsis aieicis.s 
Winter Wrens sole ccc sceciceniers aut Nannus hiemalis. 00.0. c0cc00se cess 
Brown Creeper iisteeccpe were aeiereionisens Certhiafamiliaris americana......... bs 
White-breasted Nuthatch............ Sttia COrOUMENSIS .. oi a6 cece cece ers * 
Red-breastedNuthatch.............. Silla CONGHENSIS .... cece ence neeeees 
Black-capped Chickadee.............Penthestes atricapillus..........0+4- 
Hudsonian Chickadee............... Penthestes hudsonicus littoralis....... = 
Golden-crowned Kinglet............. REGULUS SOLA PG. os ayercreys ors c's olsie® 
Hermit Thrush yeh. o-scvcteisis cones Geers = Hylocichla guttata pallast...........- 
Golden-crowned Kinglet............. Regulus SQHOPC...0...0.00cece nee 
Flermits@hrush® =< ccevcyss sere sone Hylocichla gutta pallasit.........4¢ ws 

* = records furnished by Mr. Arthur H. Norton. 

Table VI 

Biotic Data 

Amphibians and Reptiles from the Lower Stations of Mount Ktaadn 
Common Name Scientific Name Remarks 

Spotted Salamander........ Ambystoma maculatum (Shaw).....Tadpoles 
Salamander) .isct-ce acces Eurycea bislineata (Green)........ Adults 
Common toad.............Bufo americanus Holbrook. ....... Adults and tadpoles 
Green=frog. cc c6c0.eseen = Rana clamitans Latreille.......... bs 
Wood-froee.ciccucc« sete os Rana sylvatica LeC.. .. 0... .. 0000s ~ 


Common Garter Snake..... Thamnopsis sirtalis (L.).......+005 be 


471] A COMPARISON OF ANIMAL COMMUNITIES—BLAKE 107 


Table VII 
Soil Data 
Soil Sample from Coniferous Forest at Orono 
Organic and 
volatile Clay 
Depth Dry substances Ash Organic Cc.n/100 and 
of Water Matter indrymat- % andvola- NaOHper Silt Sand 
Sample % % ter, % tileN,% 10grams % 
Sin 26.95 73.05 46.25 26.80 1:25 0.7 66.7 33.3 
100 parts dry matter contain 
Organic and volatile Ash Nitrogen in organic matter 
8in 63.3 36.7 2.71 


Quantity of water in relation to dry matter is probably not significant, for although the 
samples were kept in a tightly covered can until analyses could be made, a considerable 
time elapsed before this could be done, and some water loss may have taken place. 


Table VIII 
Temperature Data 
Temperature in ground under dead leaf stratum of coniferous forest. 


Week Abs Abs Mean Mean Mean Total Mean 
Ending Max Min Max Min Temp Range Range 
June 30 15.6 9.4 13.6 11.3 12.4 6.2 2:3 

July 7 15:37 10.6 14.0 11.6 13.0 5.1 2.4 

July 14 18.3 12,5 16.0 14.7 1542 5.8 1.3 

July 21 15.8 11.4 14.4 11.8 13.5 4.4 226 

July 28 16.7 Ae 7, 15.6 13.4 13.3 5.0 262 
*Aug 4 16.7 137 15.9 1353) 14.1 5.0 2:6 

Aug 11 18.3 10.6 16.9 14.0 15.3 ted 2.9 

Aug 18 18.1 11.7 15.8 1353 14.6 6.4 2.5 

Aug 25 15.6 10.9 13.9 4 ey T1322 4.7 D2 
*Sept 1 17.0 13.9 16.0 14.2 15.2 S.1 2.0 


* Figures based on data for less than seven days 


Table IX 
Temperature Data 
Temperature in dead leaf stratum on ground in coniferous forest 


Week Abs Abs Mean Mean Mean Total Mean 
Ending Max Min Max Min Temp Range Range 


*July 21 16.1 13.3 15.5 13.3 14.5 2.8 2.2 
July 28 17.2 12:2 15.5 13.6 14.5 5.0 1.9 
Aug 4 21.1 12.2 16.6 13.3 15.6 8.9 3.3 
Aug 11 22.2 12.2 18.0 15.0 16.7 10.0 3.0 
Aug 18 17.8 12.2 15.6 13.4 14.5 5.6 2.2 
Aug 25 15.6 12:2 14.2 13.1 13.9 3.4 1.1 
*Sept. 1 17.0 14.4 16.1 15.0 15.6 2.6 12 


* Figures based on data for less than seven days. 


108 

Week Abs 
Ending Max 
June 16 23.3 
June 23 28.4 
June 30 29.4 
July 7 28.9 
July 14 30.0 
July 21 OH fed} 
July 28 PN ED 


*Aug 4 28.1 
Aug 11 29.8 
Aug 18 23:9 
Aug 25 23:3 

*Sept 1 26.1 


ILLINOIS BIOLOGICAL MONOGRAPHS 


Abs 


a 
a 


AntnNuUIrwn or 
IOAWMOWNON 


_ 
n 
Oo 


Table X 


Temperature Data 
Temperature .6 meter above the surface of the ground in coniferous forest 


Mean 
Max 


10.6 
21.7 
24.8 
22.9 
24.9 
20.4 
22.8 
22)7 
24.7 
19.4 
18.7 
21.1 


Mean 
Min 
7.7 
14.9 
13.3 
13.4 
18.3 
14.6 
14.5 
13:2 
16.0 
12.8 
12:2 
16.8 


Mean 
Temp 
8.8 
17.9 
16.2 
17.8 


Ae 
ali fe 


2 
1 


19.6 


17. 
20. 
15. 
15. 


6 
0 
7 
1 


18.6 


* Figures based on data for less than seven days 


Temperature Data 


Table XI 


Total 
Range 
2251 
23.9 
20.5 
21.7 
16.7 
19.4 
19.4 
22.8 
24.2 
16.9 
16.6 
11.1 


\472 


ra 


RPANAWOAUAOKA 
Wanna nwoanan nN oo 


Temperature 11 meters above the surface of the ground in coniferous forest 


Week Abs Abs 
Ending Max Min 


June 16 22.2 6.1 
June 23 25.0 6.7 
June 30 27.8 
July 7 27.3 
July 14 27.8 
July 21 26.7 
July 28 27.8 
Aug 4 28.3 
Aug 11 30.6 
Aug 18 22.8 
Aug 25 22.8 
*Sept 1 26.7 16.1 


RRR — 


a 
coNNTOOWO SO 


0 
4 
=) 
0 
0 
8 
we 
a2 
3 


Mean 
Max 


1c t 
22.8 
22.1 
24.1 
25.4 
DRURY 
25.5 
24.8 
27.9 
217 
20.6 
23.2 


Mean 
Min 
10.3 
10.0 
12.5 
13.3 
16.1 
13.4 
13.9 
12.0 
16.8 
11.6 
1222 
16.7 


Mean 
Temp 


13.6 
15.4 
16.8 
17.0 
20.5 
17.2 
18.5 
18.1 
2121 
1532 
15.9 
18.9 


Base Total Mean 
Mean Range Range 
11.7 16.1 8.8 
12.5 18.3 12.8 
14.4 17.8 9.6 
13.9 17.9 10.8 
18.2 13.9 9.3 
15.3 16.7 8.3 
16.3 17.8 11.6 
15:5 20.5 12.8 
17.9 18.4 11-1 
13.9 15.6 10.1 
13.4 14.5 8.4 
17.8 10.6 6.5 


* Figures based on data for less than seven days 


Week Abs 
ending Max 


June 16 100.0 
June 23 96.0 
June 30 100.0 
July 7 98.0 
July 14 100.0 
July 21 100.0 


Abs 

Min 
31.0 
44.0 
45.0 
56.0 
38.0 
36.0 


Table XII 
Humidity Data 
Relative humidity .6 meter above the surface of the ground in coniferous forest 


Mean 
Min 


Mean 
Max 


81.8 
93.1 
83.7 
89.4 
83.0 


65.2 
76.0 
75.0 
77.5 
69.8 


Mean 
R. H. 


77.4 
(es) 
84.5 
92.5 
84.9 
76.4 


Total 
Range 
69.0 
52.0 
45.0 
42.0 
62.0 
64.0 


Mean Range 
above Base 


ran 
an 
n 


aAnNnrIwWoUuoanonrsw 
wWrROoOnNWA NN KH NP 


Mean 
Range 


1 
1 


Were oan 
NOTRE DW 


1 
1 


473] A COMPARISON OF ANIMAL COMMUNITIES—BLAKE 109 


July 28 100.0 45.0 96.7 74.2 85.4 55.0 eae 
*Aug 4 98.0 40.0 90.5 68.0 79.2 58.0 22.9 
Aug 11 100.0 48.0 85.8 62.8 74.4 52.0 23.0 
Aug 18 100.0 44.0 99.0 71:1 85.0 56.0 27.9 
Aug 25 100.0 49.0 94.2 74.4 84.3 51.0 19.8 
*Sept 1 100.0 58.0 90.7 42.0 17.0 


* Figures based on data for less than seven days 


Table XIII 
Humidity Data 
Relative humidity 11 meters above the surface of the ground in coniferous forest 
Week Abs Abs Mean Mean Mean Base Total Mean Mean Range 
ending Max Min Max Min R.H. Mean Range Range below Base 
June 16 82.0 31.0 74.1 44.6 62.5 65.6 51.0 29.5 20.4 


*June 23 95.5 30.0 92.9 35.6 71.3 65.5 65.5 57.3 23.9 
June 30 100.0 27.0 89.4 49.7 69.7 79.3 73.0 39.7 29.1 
July7 99.0 31.5 98.8 41.7 74.2 93.4 67.5 57.1 51.6 
July 14 100.0 23.0 94.9 48.1 74.2 82.5 77.0 37.8 34.4 
July 21 100.0 27.0 77.2 27.0 72.6 86.2 73.0 50.2 40.0 
July 28 100.0 33.0 98.6 46.0 75.7 87.3 67.0 52.6 41.4 
Aug 4 100.0 22.0 97.6 37.0 73.1 85.4 78.0 60.6 40.7 
Aug11 100.0 34.0 97.6 44.3 77.9 87.3 66.0 53.3 42.9 
Aug 18 100.0 31.0 99.0 55.3 84.8 96.2 69.0 43.7 40.2 
Aug 25 100.0 26.0 98.6 56.3 81.0 92.3 74.0 42.3 36.3 
*Sept1 100.0 41.0 95.0 63.8 81.8 92.6 59.0 31.2 27.8 


* Figures based on data for less than seven days 


Table XIV 

Evaporation Data from Pine Forest, Obtained with Porous Cup Atmometers 

Sta No 1 2 3 4 5 6 7 8 9 
Height (M) 120) -£.0% 50:37 «2.5 0:3: 6:5 17,0), 033 
Date (wk.) Average daily evaporation in cc. (reduced to standard) 
June 23 * * * * * * * * 
June 30 10.4 9.5 7.2 12.5 0.9 5.4 17.7 18.8 
July 7 12.3 10.0 16.9 0.4 }f6.9 21.8 23.7 bd 
July 14 14.3; 12.1. 19.6 0.2 Qi.O0 27.2 18.55 
July 21 i 13.7 9.6 18.9 0.3 25.5 26.8 18.8 
July 28 14.4 13.6 11.7 18.4 0.3 23.8 26.4 16.2 
Aug 4 15.4 * 19.2 0.3 25.1 26.8 15.8 
Aug 11 7.8 4.4 10.2 0.04 13.0 13.1 ¢ 
Aug 18 6.0 4.3 8.1 0.03 10.5 10.6 
Aug 25 ico 5.0 10.1: 0,04 14.6 15.4 


* The date on which a given atmometer was placed in position, and marks the beginning 
of the evaporation which was recorded one week later. 


{ This instrument was moved on July 7 to Station No. 9 
} This instrument was destroyed, and no further observations were taken at the station 


110 ILLINOIS BIOLOGICAL MONOGRAPHS [474 


Table XIVa 
Location of Stations 

1 Black atmometer sphere, exposed on specially constructed 

stand 2 meters from instrument shelter 
2 White atmometer sphere, exposed with No. 1 
3 White atmometer sphere, on ground under shrubs, near Nos. 

1 and 2 
4 White atmometer sphere, suspended from lower branch of 

small hemlock 
5 White atmometer sphere, placed in an observation cavity 
dug in the soil, and covered with a grating on which was 
placed the usual layer of pine needles and other forest 
floor debris; the sphere was just beneath this mat 
White atmometer sphere, on ground in swampy glade; long grass 
White atmometer sphere, in pine tree 
White atmometer sphere, at level of upper branches 
White atmometer sphere, on ground at western forest margin, among 
shrubs and weeds,. but exposed to wind over short grass area 


woonn 


Table XV 
Summer Variations in Light Intensity in Pine Forest, as Measured with a Wynne 
Exposure Meter August 6-8, 10-13, 15-19, 21-23, 25, 27, 1924 
On the Ground 
Date Time Reading Weather Conditions 
in Sec 
Aug 6 3:11PM 80.0 Sun shining through light clouds 
Aug 7 2:17PM 60.0 Clear 
Aug 8 2:00 P M 67.0 Clear 
Aug 8 2:12 PM 158.0 Sun shining through light clouds 
Aug 10 2:09 PM 170.0 Fair; sun shining through light clouds 
Aug 11 2:01 PM 180.0 Clear; sun shining through light clouds 
Aug 12 2:48 P M 487.5 Cloudy; very dull and raining 
Aug 13 1:20 P M 125.0 Fair 
Aug 15 1:16 PM 235.0 Clear; diffused light 
Aug 16 2:09 P M 281.0 Diffused light 
Aug 17 1:46 PM 271.0 Diffused light shining through clouds 
Aug 18 1:06 P M 175.0 Fair; sun shining through light clouds 
Aug 19 3:22PM 2100.0 Very dull; raining heavily 
Aug 21 2:25PM 354.5 Dull 
Aug 22 1:58 P M 515.0 Very dull 
Aug 23 1:44 P M 470.0 Cloudy and dull 
Aug 25 2:21PM 570.0 Cloudy and very dull 
Aug 27 2:53PM 461.0 Cloudy 


Table XVI 
Summer Variations in Light Intensity in Pine Forest, as Measured with a Wynne 
Exposure Meter August 6-8, 10-13, 15-19, 21-23, 25, 27, 1924 
1.5 meters above Ground 
Date Time Reading Weather Conditions 
in Sec 

Aug 6 3:14 P M 33.0 Sun shining through light clouds 
Aug 7 2:19 P M 14.5 Clear 


475] A COMPARISON OF ANIMAL COMMUNITIES—BLAKE 


Aug 8 2:03 P M 39.0 Clear 

Aug 8 2:15 PM 127.5 Sun shining through light clouds 
Aug 10 2:13 PM 147.0 Fair; sun shining through light clouds 
Aug 11 2:05 PM 162.0 Clear; sun shining through light clouds 
Aug 12 2:48 P M 240.0 Cloudy; very dull and raining 

Aug 13 1:25P M 83.0 Fair 

Aug 15 1:19 P M 94.0 Clear; diffused light 

Aug 16 2:12PM 89.0 Diffused light 

Aug 17 1:51PM 196.0 Diffused light shining through clouds 
Aug 18 1:10PM 143.0 Fair; sun shining through light clouds 
Aug 19 3:332 PM 420.0 Very dull; raining heavily 

Aug 21 2:37 PM 211.5 Dull 

Aug 22 2:02 PM 220.0 Very dull 

Aug 23 1:48 PM 114.0 Cloudy and dull 

Aug 25 2:31 PM 420.0 Cloudy and very dull 

Aug 27 2:09 P M 90.0 Cloudy 


Table XVII 
Summer Variations in Light Intensity in Pine Forest, as Measured with a Wynne 
Exposure Meter August 6-8, 10-13, 15-19, 21-23, 25, 27, 1924 
In Open Glade 


Date Time Reading Weather Conditions 

in Sec 
Aug 6 3:20 P M 15.0 Sun shining through light clouds 
Aug 7 2:23 PM 12.0 Clear 
Aug 8 2:06 P M 16.0 Clear 
Aug 8 2:18PM 47.0 Sun shining through light clouds 
Aug 10 2:17PM 25.0 Fair; sun shining through light clouds 
Aug 11 2:21 PM 30.0 Clear; sun shining through light clouds 
Aug 12 2:02 PM 90.0 Cloudy; very dull and raining 
Aug 13 1:28 P M 30.0 Fair 
Aug 15 1:23 P M 56.0 Clear; diffused light 
Aug 16 215 P Mi 65.0 Diffused light 
Aug 17 1:55 PM 39.0 Diffused light shining through clouds 
Aug 18 1:12PM 45.0 Fair; sun shining through light clouds 
Aug 19 3:37 PM 90.0 Very dull; raining heavily 
Aug 21 2:40 P M 47.0 Dull 
Aug 22 2:02 PM 61.0 Very dull 
Aug 23 1:48 P M 33.0 Cloudy and dull 
Aug 25 2:50P M 83.0 Cloudy and very dull 


Aug 27 2:21PM 37.0 Cloudy 


Table XVIII 


Summer Variations in Light Intensity in Grassland Adjoining Pine Forest, as Meas- 
ured with a Wynne Exposure Meter August 6-8, 10-13, 15-19, 21-23, 25, 27, 1924 
On the Ground 


Date Time Reading Weather Conditions 
in Sec 

Aug 6 3:27 PM 4.0 Sun shining through light clouds 

Aug 7 2:28 PM 3.0 Clear 


Aug 8 2:09 PM 3.0 Clear 


111 


Animal population of coniferous forest, considered by strata and as a whole, 


Date 


Jul 7 
Jul 21 
Jul 28 
Aug 11 
Aug 14 
Aug 18 
Aug 21 
Aug 25 
Sept 1 


Animal population of deciduous forest, considered by strata and as a whole, 


Week Soil Str Leaf 
ending Coll Ave 


ILLINOIS BIOLOGICAL MONOGRAPHS 


2:21PM 
2:20P M 
2:24 P M 
2:57 PM 
1:32 PM 
1:26PM 
2:17PM 
1:58 PM 
1:15 PM 
3:40 P M 
2:42PM 
2:07PM 
1:54 P M 
2:53 PM 
2:23 PM 


Soil Str 


Coll Ave 


tl a Oe Ot 9 


4 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 


18 
13 
5 
16 
11 
17 
8 
6 
4 


pee 


to 


an 
ANDONNDOONADWOwMwW 
oooooooooconooocno 


e 


eR 


Sun shining through light clouds 
Fair; sun shining through light clouds 
Clear; sun shining through light clouds 
Cloudy; very dull and raining 


Fair 


Clear; diffused light 


Diffused light 


Diffused light shining through clouds 
Fair; sun shining through light clouds 
Very dull; raining heavily 


Dull 
Very dull 


Cloudy and dull 
Cloudy and very dull 


Cloudy 


Table XIX 
Biotic Data 


July 7 to Sept. 1, 1924 


Leaf Str 
Coll Ave 
1 9 

2 37 

2 8 

1 15 

1 21 

I 34 

2 44 

1 11 

1 21 


Herb Str 
Coll Ave 


44 
14 
95 
23 
30 
34 
15 
79 
40 


BPR RP Re Ree dt 


Table XX 
Biotic Data 


Shrub 
Coll 


me WR RE Redd 


Str 
Ave 


32 
26 
18 


October 6, 1924, to March 2, 1925 


Str 
Coll Ave 

16 3 81 
68 1 42 
10 1 48 
48 2 59 
11 1 124 
10 1 74 
37 3 196 
20 2 87 
21 ff! 165 
18 1 15 
37 1 28 


Herb Str 
Coll Ave 


Lee eel ee ee oe cee cee oe ee eS) 
ra 
cs 


Shrub 
Coll 


ll aos) 


Str 
Ave 


46 
41 
27 
13 


COPROrRPNMNM 


[476 


Total Per Per 
Acre Hectare 
(Thousands) 

103. 1,121 3,039 

90 980 2,656 

126 =: 11,426 3,864 

96 =1,045 2,831 

76 827 2,241 

118 =: 1,285 3,482 

83 903 2,447 

140 =—-:1,524 4,130 

106 =: 1,154 3,127 

Total Per Per 
Acre Hectare 
(Thousands) 

183 1,992 5,400 

228 2,482 6,728 

109 1,187 3,216 

127. 1,383 3,748 

174 1,894 5,135 

100 1,089 2,951 

241 2,624 7,112 

108 1,176 3,187 

198 2,156 5,843 

33 359-973 

65 707 =1,203 


477] A COMPARISON OF ANIMAL COMMUNITIES—BLAKE 113 


Jan 5 i 26 1 
Jan 12 1 20 1 
Jan 19 1 28 1 
Jan 26 1 15 1 
Feb 2 1 24 1 
Feb 9 1 9 1 
Feb 16 1 23 1 
Feb 23 1 37 1 
Mar 2 1 30 1 


ing trees. 


78 
25 
53 
37 
64 


ee 
oaorooococoe 


Table XXI 
Winter Bird Census of Cottonwood (January 5-March 2, 1925) 


The forest margin is characterized by presence of thick growths of bushes and is ad- 
jacent on three sides to fields of corn. The interior is characterized, throughout the greater 
part of its extent, by absence both of bushes dense enough to afford shelter and of low branch- 


104 
45 
81 
52 
88 

343 

155 

304 
31 


ee 
Oororoooc]e 


1,132 3,059 
490 1,328 
882 2,388 
571 1,549 
958 2,597 


3,735 10,122 
1,687 4,574 
3,310 8,971 
337914 


In the third column of the following lists M indicates forest margin; I indicates interior. 


Name 


Slate-colored junco 
(Junco hyemalis) 
Tree Sparrow 
Spizella monticola 
Tufted titmouse (Bae 
olophus bicolor) 


Blue jay (Cyanocitta 
cristata) 
Northern flicker 
(Colaptes auratus 
luteus) 
Cardinal (Cardinalis 
cardinalis) 


Downy woodpecker (Dry- 


obates pubescens medi- 
anus) 
Hairy woodpecker (Dry- 
obates villosus) 
Red-bellied woodpecker 
(Centurus carolinus) 


Species are listed in order of abundance 


I. Species Always Present 


Esti- Loca- 
mated tion 
Number 
15 M(I) 
10 M 
8 I(M) 
5 I(M) 
5 I,M 
592 IM 
93 
3011 I,M 
291 IM 
1 I 
Table XXII 


Biotic Data 


Stratum 


Bushes, ground; 


Remarks 


In flocks, often 


trees rarely with tree sparrows 


Bushes, ground 


Tree tops, bush- 
es rarely 


In flocks of 
juncos 


Often in flocks 
of 3 to 5 


Trees oftenest, | Very conspicuous, 


bushes, ground 


Trees 


Trees, bushes 


often in flight 


Often in flight 


Trees 
Trees 

Conspicuous until 
Trees last week of Jan. 


Winter Bird Census of Cottonwood 


The individuals of the first two species listed doubtless changed from day to day, as 
flocks of juncos and tree sparrows were seen frequently crossing the fields to and from the 
forest. The numbers of column two represent an estimate of the number of individuals 


Not seen later 


114 ILLINOIS BIOLOGICAL MONOGRAPHS 


[478 


which could practically always be found by hunting throughout approximately the same 
parts of the forest. The numbers given are based on the daily records but are an estimate, 
inasmuch as it was never possible, on one day, to study all parts of the forest with equal 
thoroughness; also it was difficult to be absloutely certain, in the case of such birds as the 
titmice and the blue jays, how much allowance to make for “repeaters” in the day’s record. 

The first three species listed appeared occasionally in much larger flocks. Blue jays 
and northern flickers were more numerous than the census indicates on a few warm days 
in February, when they formed small flocks (each with its own species). 


Species Frequently Present 


Name Estimated Location . Stratum 
Number 

American crow (Corvus brachy- 

rhynchos) 5 I Above trees 

Chickadee (Penthestes atrica- 

pillus) 2 M(I) Bushes, trees 

Hawks (probably Buteo, at 

least 2 species) 1 M,I _ tween trees 

(Trees) 

Table XXIII 
Biotic Data 


Winter Bird Census of Cottonwood 
Species Occasionally Present 


Name Esti- Loca- Stratum 
mated tion. 
Number 
Bob-white (Colivenus virgin- 
tanus) 6 I Ground 
Mourning dove (Zenaidura 4 M Ground, low 
macroura carolinensis) branches 
English sparrow (Passer do- 4 M Tree 
mesticus) 
Redpoll (Acanthis linaria li- 29 M 
naria) 
Goldfinch (A stragalinus tristis) 10 M Above trees 
Golden crowned kinglet (Reg- 1 I Ground 
ulus satrapa) 
Migrant shrike (Lanius ludo- 1 M Tree 


vicianus) (var. migrans) 

Bronzed grackle (Quiscalus 1 
quiscula aeneus) 

White-breasted nuthatch (Sir- 1 
ra carolinensis) 


Above trees 


Remarks 


In flight 

ges 
With juncos, usually 
at margin 


Above and be- In flight usually, tree- 


tops rarely 


Remarks 


Under fallen, leafy 
trees. Only in very 
cold weather 

Once only 


Once only, though 
abundant at farmyard 
opposite 


Bushes, ground Once only in flock 


with juncos and tree 
sparrows. (Probably 
more common.) 

In flight, across edge 
of forest. Once only 
Once only 


Once only 
In flight across forest. 


Once only 
Once only heard 


479] A COMPARISON OF ANIMAL COMMUNITIES—BLAKE 115 


Table XXIV 


Biotic Data 
Winter Bird Census of Cottonwood 
Spring Migrants 


Name Estimated Location Stratum Earliest Remarks 
Number Date 

Robin  (Planesticus 2 to 25 I,M __ Trees, ground; Feb 16 The larger number 

migratorius) above trees in flocks. Often in 
flight 

Rusty blackbird (Eu- 6 to 18 I,M__ Trees, bushes, Feb 27 Tn flocks 

phagus carolinus) (92) ground 

Red-winged blackbird 1or 2 M Trees, bushes Mar 2 With flocks of rusty 

(Agelaius phoeniceus) blackbirds 

Bluebird (Sialia sialis) Feb 8 Once only in forest 
until after three 
weeks of cold weath- 


er with which win- 

ter study closed. 

Some of the birds of the list above, instead of being strictly migrants, may have been 

individuals which had wintered in this latitude in sheltered retreats from which they appeared 

on favorable days. A few also were probably early summer residents, as in the case of the 

robins who, after their first appearance, were always present to the number of two or three 
in the forest. 


XXV 
Biotic Data 
Winter Birds of Cottonwood, January, 1925 


The following list states the number of individuals of each species seen on the date 


given. 
January 5 12 19 21 23 24 26 29 31 


Quail (Colinus virginianus)....... _ —_ _ — 6bor8 — — — — 
Mourning Dove (Zenaidura)...... — — — _ _ — = — 
Hawks (large) lene cease eyoisenieves.cteoa:2 —_ 

(Buteo borealis) 

(Buteo lineatus) probably both 
Hairy woodpecker (Dryobates vil- 

LOSUS) Wenets ys reeravlasslanaisc-¢.c frase esd = — aa = a 19 «4 — 1 
Downy woodpecker (Dryobates 

pubescens medianus).........4.+% — — 3 —= 2 2 1 1 —_ 
Red-bellied woodpecker (Centurus 

carolinus) 1 — 
Flicker (Colaptes auratus luteus)... .. — = 
Blue jay (Cyanocitta cristata)....... 3 3 
Crow (Corvus brachyrhynchos)...... 2 —— 
Bronzed Grackle (Quiscalus quis- 

CULO CENCUS) vactalsiscxe cose aves tea — _ 1 = —_— — — _ —_ 
Tree sparrow (Spizella monticola)....— — — 10 10 == = — 
Junco (Junco hyemalis)............ — — 15 5 
Cardinal (Cardinalts cardinalis).....— 1 39 12 2(19)— — —3 (19 


es 
NR 

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116 ILLINOIS BIOLOGICAL MONOGRAPHS 


Migrant shrike (Lanius ludovicianus 

TMIGTANS) ly: ore: acave, vare'e-ehelsiereiwie Feiaien — —_ _ ood _ 1 _— 
Tufted titmouse (Baeolophus bicolor) 4 _ 
Chickadee (Penthestes atricapillus).. 1 —_— _— — — — —_ 
Golden-crowned kinglet (Regulus 

SQUGDG) wicca swaentacn satietoleeea wets 1 _ _— _ _ _— _— 
English sparrow (Passer domesticus) .— — _— _ — _ —_— 


» 
wn 
w 
ioe) 
w 


Birds of Cottonwood, February 2 to March 2 (Inclusive) 


[480 


n 


The following list states the number of individuals of each species estimated to be 


present on the given date. 
F2 6 8 9 13 16-23 


Hawk (large) (Buteo sp.)......... 1 _— 1 _— _ _ _ 
Hairy woodpecker (Dryobates vil- 

LOSUS) eiio08s Sea eee eae ae — _ _ 1 17 1 — 
Downy woodpecker (Dryobates 

pubescens medianus).........0+5 20 
Flicker (Colaptes auratus luteus)... 8 
Blue jay (Cyanocitta cristata). ..... 5 
Crow (Corvus brachyrhynchos)..... = 
Red-winged blackbird (A gelaius 

PHOCKIGEUS) Sock cece odes 6 _> — a a 
Rusty blackbird (Euphagus caro- 

LINUS) is vacireic Saree emfersoe eee ak _ _— _ _— _— _ = 
Redpoll (Acanthis linaria linaria). .— = = = = — 29 
Goldfinch (A stragalinus tristis). ...— = = — — = = 
Tree sparrow (Spizella monticola). .10 _ _ _ — _ 20 
Slate-colored junco (Junco hye- 

MANS) clecitasnrersargterdarvas sass’ 100 — 20 10 8 10 
Cardinal (Cardinalis cardinalis)... 2 532 — — — _ 2 
White-breasted nuthatch (Sitta car- 

OUMENSIS) stare: 0 alae seteteyeroisoies — — 1(heard only) — _ 
Tufted titmouse (Baeolophus bi- 

COLON) cs sre aeaiisie wens ete 7 20 6 8 12 
Chickadee (Penthestes stricapillus)—  — _ 2 Te 
Robin (Planesticus migratorius)...— — _ _ — 2 3 
Bluebird (Sialia sialis)........... — _— 1(Species report only) 


Creo | 
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1 = 
5 15 
2 4 
—1lor2 
18 69 
— 10 
— 3 
10 18 
19 2 
9 3 
2 2 
15 26 


481] A COMPARISON OF ANIMAL COMMUNITIES—BLAKE 117 


PLATE I 


118 ILLINOIS BIOLOGICAL MONOGRAPHS [482 


EXPLANATION OF PLATE I 


1. Station C, at an elevation of 5,080 feet on the Table-land of Mount Ktaadn. The char- 
acteristic vegetation consists of various grasses and sedges. 

2. Station D. Krummholz. 

Station F. Pond-bog habitat; Pamola Pond, 2,700 feet elevation. 


Ww 


ILLINOIS BIOLOGICAL MONOGRAPHS VOLUME X 


BLAKE PLATE I 


483] A COMPARISON OF ANIMAL COMMUNITIES—BLAKE 119 


PAE. UL 


120 ILLINOIS BIOLOGICAL MONOGRAPHS [484 


EXPLANATION OF PLATE II 
4, Interior of coniferous forest at Orono, Maine, showing the exposure of instruments. 
The instrument shelter contained a thermograph and a hygrograph, which were thus 
raised to a height of 11 m above the surface of the ground. An atmometer may be seen 
in a bracket on the shelter and another hanging from the shelter, 6 m above the ground. 


The deciduous forest habitat at Urbana, Illinois, as it appeared during much of the winter 
study. 


VOLUME X 


ILLINOIS BIOLOGICAL MONOGRAPHS 


PLATE II 


BLAKE 


485] A COMPARISON OF ANIMAL COMMUNITIES—BLAKE 121 


PLATE III 


122 ILLINOIS BIOLOGICAL MONOGRAPHS [486 


EXPLANATION OF PLATE III 


Map of Upper Regions of Mount Ktaadn 
(After sketch map by Parker B. Field, published by the Appalachian Mountain Club.) 
Fig. 6. Ecological stations as follows: 
Station A—Rock Animal Community 
Station C—Tundra Animal Community 
Station D—Krummbholz Animal Community 
Station E-2—Upper Climax Forest Animal Community 
Station E—Lower Climax Forest Animal Community 
Station F—Pond-bog Animal Community. 


ILLINOIS BIOLOGICAL MONOGRAPHS VOLUME X 


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487] A COMPARISON OF ANIMAL COMMUNITIES—BLAKE 123 


PLATE LV 


124 ILLINOIS BIOLOGICAL MONOGRAPHS [488 


EXPLANATION OF PLATE IV 


7. Maximum and minimum temperatures at Chinney Pond on Mt. Ktaadn. D=day, 
N=night. 

8. Maximum and minimum daily temperatures at Basin Pond on Mount Ktaadn. 

9. Hythergraphs of localities under consideration. 
The horizontal scale shows precipitation in inches, the vertical temperature in degrees 
Centigrade. The broken curve represents the conditions of precipitation and temper- 
ature at Ft. Chimo, Ungava. The graph which is ruled horizontally is for Orona, 
Maine. That which is ruled vertically is for Mt. Washington, New Hampshire. 


ILLINOIS BIOLOGICAL MONOGRAPHS 


VOLUME X 


tboetoaseszouezb ey ezbauebes 


PLATE IV 


VOLUME X 


ILLINOIS BIOLOGICAL MONOGRAPHS 


PLATE IV 


BLAKE 


489] A COMPARISON OF ANIMAL COMMUNITIES—BLAKE 125 


PLATE V 


126 ILLINOIS BIOLOGICAL MONOGRAPHS [490 


EXPLANATION OF PLATE V 


10. Weekly mean temperatures at various strata of the coniferous forest habitat. 
A=Temperature 0.6 m above the ground. 
B=Temperature 11 m above the ground. 
C=Temperature in the ground, under the mat of dead leaves. 
D=Temperature in the mat of dead leaves. 
All temperatures are centigrade degrees, with a base at 10°, and horizontal rulings at 
15°, 20° and 25°, respectively. Each Centigrade degree is indicated by smaller divisions 
on the lateral margins. 
The mean temperatures for the weeks ending June 16, 23, and 30, July 7, 14, 21 and 28, 
August 4, 11, 18 and 25, and September 1, are indicated by the labels and divisions 
at the upper and lower margins. The records for some of the strata were not begun 
until the study had been progressing some time. 

11. Weekly mean variations of temperatures at various strata of the coniferous forest 
habitat. 
A=Variation in temperature 0.6 m above ground. 
B=Variation in temperature 11 m above ground. 
C=Variation in temperature in ground, under dead leaf stratum. 
D=Variation in temperature in dead leaf stratum. 
Notations similar to those used in 1. The base-line is at 0°C; horizontal rulings indicate 
5°, 10° and 15°C. 

Humidity Data 

12. Weekly mean relative humidity at two levels in the coniferous forest habitat: 0.6 m 
(A) and 11 m (B) above the ground. 
Divisions on the upper and lower margins indicate the weekly intervals. Horizontal 
rulings are placed at each 10% of relative humidity, with a base-line drawn at 60% and 
the top line representing 100% relative humidity. 

13. Weekly mean variations in relative humidity at two levels in the coniferous forest 
habitat: 0.6 (A) and 11 m (B) above ground. 
The base-line is 0% relative humidity, and the horizontal lines above stand for additional 
increments of 10% relative humidity up to 70%. 


VOLUME X 


ILLINOIS BIOLOGICAL MONOGRAPHS 


ony Be Te 


Fr LAINE OF 


&@ 


Or aunge 


PLATE V 


BLAKE 


491] A COMPARISON OF ANIMAL COMMUNITIES—BLAKE 127 


PLATE V1 


128 


14. 


15. 


ILLINOIS BIOLOGICAL MONOGRAPHS [492 


EXPLANATION OF PLATE VI 
Evaporation Data from Pine Forest 


Evaporation from porous cup atmometers at stations 2, 3, 4, 5, 7 and 8, in mean 
Daily Evaporation per week. 

The vertical scale is divided into increments of 1 cc, with horizontal lines drawn at 
5, 10, 15, 20 and 25 cc. The vertical scale is divided according to weeks. 
Each curve is numbered according to the station where it was recorded. 

Diagram showing the comparative amount of evaporation, in terms of the daily mean, 

spherical porous cup atmometers at eight stations (No. 2 to No. 9) in the habitat. 
The data covers the Nine Week Period. 
The scale is divided into vertical increments, showing a range of evaporation of from 
0 cc to 21 cc, expressed in terms of the daily mean for the period of study, each division 
representing 1 cc. The columns represent the various stations, to correspond with which 
they are numbered. 


ILLINOIS BIOLOGICAL MONOGRAPHS VOLUME X 


BLAKE PLATE VI 


a 


493] A COMPARISON OF ANIMAL COMMUNITIES—BLAKE 129 


PLATE Vit 


130 ILLINOIS BIOLOGICAL MONOGRAPHS [494 


EXPLANATION OF PLATE VII 


Biotic Data 

16. Animal population, as a whole and according to strata, in coniferous forest, July 7 
to September 1, 1914. 
The divisions along the upper and lower margins represent the weeks, as in the plates 
on temperature and humidity. The divisions along the lateral margin indicate ten 
animals taken in collecting. 
A—Total population; B—Population of herb stratum; C—Population of shrub stratum; 
D—Population of leaf stratum; E—Population of soil stratum. 


ILLINOIS BIOLOGICAL MONOGRAPHS 


BLAKE 


June30 July? 14 21 28 Augd i 18 25 Septl 


L100 


60 


A 


VOLUME X 


PISA TE Vial 


i , 
a 
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7 

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Mey One 
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2 


ILLINOIS BIOLOGICAL MONOGRAPHS VOLUME X 


June30 July? I4 A 28 Auge it 18 25 Sept 


BLAKE PEAT ESViL 


VOLUME X 


ILLINOIS BIOLOGICAL MONOGRAPHS 


f E291 6 F 9Z6TEI SGBeESI & I Fe LTOT 


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BLAKE 


Alsepaie yu PeEhA aIeS 


495] A COMPARISON OF ANIMAL COMMUNITIES—BLAKE 131 


PEATE Vit 


132 ILLINOIS BIOLOGICAL MONOGRAPHS 


EXPLANATION OF PLATE VIIT 
Resident Population of the Lowest Strata 


17. Resident population of the lowest strata 
A. Helodrilus caliginosus trapezoides (Dugés) 
B. Tomocerus flavescens Tullberg var. separatus Folsom. 
b. Herb stratum 
c. Leaf stratum 
d. Soil stratum 
18. Summer Population of Arachnida 
a. Leiobunum politum Weed. 
b. Linyphia sp. (juvenile) 
c. Tetragnatha sp. (juvenile) 


[496 


ILLINOIS BIOLOGICAL MONOGRAPHS VOLUME X 


BLAKE PLATE VIII 


497] A COMPARISON OF ANIMAL COMMUNITIES—BLAKE 133 


PEARE 1X 


134 ILLINOIS BIOLOGICAL MONOGRAPHS [498 


EXPLANATION OF PLATE IX 


19. Summer Population of Homoptera 
A Clastoptera obtusa (Say) 
a. Shrub stratum 
b. Herb stratum 
B Graphocephala coccinea (Forst.) 
a. Shrub stratum 
b. Herbstratum 
20. Summer and Stratal Populations of Homoptera and Hemiptera 
A Macrosiphum coryli Davis 
B Nabis sp. (juvenile) 
C Dicyphus famelicus (Uhl.) 
a. Shrub 
b. Herb 
D Diaphnidia pellucida Uhl. 


ILLINOIS BIOLOGICAL MONOGRAPHS VOLUME X 


BLAKE PLATE IX 


499] A COMPARISON OF ANIMAL COMMUNITIES—BLAKE 135 


5 Wee PS. 


136 ILLINOIS BIOLOGICAL MONOGRAPHS [500 


EXPLANATION OF PLATE X 


21. Weekly mean temperatures at various strata of the deciduous forest habitat: 15 cm 
below the surface of the ground, 0.6 m and 11 m above the surface. 

All temperatures are Centigrade degrees, with a base at —15°, and horizontal rulings 
at — 10°, —5°, 0°, 5°, 10°, respectively, Each Centigrade degree is indicated by smaller 
divisions on the margins. 

The mean temperatures for the weeks ending November 17 and 24, December 1, 8, 
15, 22 and 29, January 5, 12, 19 and 26, February 2, 9, 16 and 23, and March 2 and 9, 
are indicated by the labels and divisions on the longer margins. A break of one week, 
that of January 12, occurs in the record taken at a height of 11 m. 

A=Temperature .6 m above ground. 

B=Temperature 11 m above ground. 

C=Temperature 15 cm below ground. 

22. Weekly mean variations of temperatures at various strata of the deciduous forest 
habitat: 15 cm below the surface of the ground, 0.6 m and 11 m above the surface. 
Scheme of representation same as in preceding plate. The base-line is at 0°C.; horizontal 
rulings indicate 5°, 10°, 15°, 20° and 25°c. 

A=Variation in temperature .6 m above ground. 
B=Variation in temperature 11 m above ground. 
C=Variation in temperature 15 cm below ground. 

23. Weekly mean relative humidity and weekly mean variations in relative humidity 
0.6 m above ground in the deciduous forest habitat. 

Divisions on the upper and lower margins indicate the weekly intervals. Horizontal 
Tulings are placed at each 10% relative humidity, with base-lines drawn at 40% for 
the weekly mean relative humidity, and at 0% for the weekly mean variations in rel- 
ative humidity. 

A= Weekly mean relative humidity 

B=Weekly mean variations in relative humidity. 


ILLINOIS BIOLOGICAL MONOGRAPHS VOLUME xX 


Novl? 24 [ecl 9 1522 29 Jon5 12 19 26 Feb2 9 16__23 Mar2 9 


Sh 


Novi? 24 Decl 9 15 22 29 Jan5 12 19 26 Feb2 9 16 23 Mar2 9 
T T T iF T T T T T r T a ed T 


22 


Novi? 24 Decl 9 15 22 29 Jan5 12 9 26 Feb2 9 16__ 23 Mar2 9 
PI T T T T T T T 7 T Sel naa Pet | Se 


B 


BLAKE PLATE X 


501] A COMPARISON OF ANIMAL COMMUNITIES—BLAKE 137 


PLATE XI 


138 ILLINOIS BIOLOGICAL MONOGRAPHS [502 


EXPLANATION OF PLATE XI 
Biotic Data 


24, Animal population, as a whole and by the two upper strata considered, in deciduous 
forest, October 6, 1924, to March 2, 1925. 
The divisions along the upper and lower margins represent the weeks, as indicated. 
The divisions along the lateral margins represent ten animals taken in collecting. 


A=Total population. 
B=Population of herb stratum. 
C=Population of shrub stratum. 
25. Animal population of the two lower strata deciduous forest, October 6, 1924, to March 2, 
1925. 
The divisions along the upper and lower margins represent the weeks, as indicated. 
The divisions along the lateral margins represent ten animals taken in collecting. 


D=Population of leaf stratum. 
E= Population of soil stratum. 


VOLUME X 


ILLINOIS BIOLOGICAL MONOGRAPHS 


@ S91 6 & 9261 CI 2 62-eeST 8 TEELIO! & Le 0@ET 9 
1D CEC uve 200 00N PO 


& &2 91 6 & 98 OTET S62 @ SIS 1 FELIOT € 
Lon Va Ud" 20 ON 


PO 


PLATE XI 


BLAKE 


hu 


503] A COMPARISON OF ANIMAL COMMUNITIES—BLAKE 139 


PLATE XII 


140 


ILLINOIS BIOLOGICAL MONOGRAPHS 


EXPLANATION OF PLATE XII 


26. Winter Populations of Spiders and Mollusks 


A 
B 


Linyphia phrygiana C. Koch 
Dictyna volupis Keyserling 


a. 
‘ } Shrub and herb strata 


c. Leaf stratum 
Anyphaena rubra Emer. (juvenile) 
a. Shrub stratum 

b. Herb stratum 

c. Leaf stratum 

Carychium exile H. C. Lea 
Zonitoides arborea (Say) 
Gastrocopia tappaniana (C. B. Adams) 
Zonitoides minuscula (Binney) 
Vitrea indentata (Say) 

c. Leaf stratum 

d. Soil stratum 

Carychium exiguum (Say) 


[504 


ILLINOIS BIOLOGICAL MONOGRAPHS VOLUME X 


9 


BLAKE PLATE XII 


505] A COMPARISON OF ANIMAL COMMUNITIES—BLAKE 141 


PEATE XII 


142 ILLINOIS BIOLOGICAL MONOGRAPHS [S06 


EXPLANATION OF PLATE XIII 


27. Winter Populations of Various Insects. 
Cantharis sp. (larva) 
Meracantha contracta (Beauv.) (larva) 
Phyllotreta sinuata (Steph.) 
Tipula sp. (larva) 
c. Leaf stratum 
d. Soil stratum 
E WNabis ferus (L.) 

a. Shrub stratum 

b. Herb stratum 

c. Leaf stratum 

d. Soil statum 
F Lygus pratensis oblineatus (Say) 

a. Shrub stratum 

b Herb stratum 

c. Leaf stratum 

d. Soil stratum 


Caw, 


ILLINOIS BIOLOGICAL MONOGRAPHS VOLUME X 


BLAKE PEATE XI 


JRE appaay 
OF THE 
DDIWARSITY OF AM LawaIS 


507] A COMPARISON OF ANIMAL COMMUNITIES—BLAKE 143 


PLATE XTV 


144 ILLINOIS BIOLOGICAL MONOGRAPHS [508 


EXPLANATION OF PLATE XIV 


28. Winter Populations of Beetles 
A Epitrix brevis Sz. 

a. Shrub stratum 

b. Herb stratum 

c. Leaf stratum 

d. Soil stratum 

Ptilodactyla serricollis (Say) 

Nitidula rufipes (L.) 

Telephanus velox Hald. 

b. Herb stratum 

c. Leaf stratum 

d. Soil stratum 

Malthodes sp. (larva) 


yvaw 


ic] 


ILLINOIS BIOLOGICAL MONOGRAPHS VOLUME X 


BLAKE PLATE XIV 


. 1 7 
Abie b oh thet 


CrmaAL 


Fi thee ak eye Mk gidet 
a 
= 


509] A COMPARISON OF ANIMAL COMMUNITIES—BLAKE 145 


PLATE XV 


146 ILLINOIS BIOLOGICAL MONOGRAPHS [510 


EXPLANATION OF PLATE XV 


29. Winter Population of Collembola 


A Onychiurus fimetarius (L.) 
B Onychiurus armatus Tullberg 
C Isotoma sp. 
c. Leaf stratum 
d. Soil stratum 
D Onychiurus subtenuis Folsom. 


30. Winter Populations of Collembola and Enchytraeidae 


A Tomocerus flavescena Tullberg var. americanus Schott 
b. Herb stratum 
c. Leaf stratum 
d. Soil stratum 
B_ Enchytraeidae 
c. Leaf stratum 
d. Soil stratum 


ILLINOIS BIOLOGICAL’ MONOGRAPHS VOLUME X 


[ 


Jan 


Dec 
1 


BLAKE PLATE XV 


511] A COMPARISON OF ANIMAL COMMUNITIES—BLAKE 147 


BiAt Ee Ova 


148 ILLINOIS BIOLOGICAL MONOGRAPHS [520 


EXPLANATION OF PLATE XVI 


31. Winter Populations of Myriapods and Diptera 
A Linotaenia chionophila (Wood) 
c. Leaf stratum 
d. Soil stratum 
B_ Pokabius bilabiatus (Wood) 
c. Leaf stratum 
d. Soil stratum 
C  Cleiodogona caesioannulata (Wood) 
c. Leaf stratum 
d. Soil stratum 
D Fontaria virginiensis Dru 
c. Leaf stratum 
d. Soil stratum 
E Scytonotus granulatus (Say) 
c. Leaf stratum 
d. Soil stratum 
F Leptocera sp. 
a. Shrub stratum 
b. Herb stratum 
c. Leaf stratum 
d. Soil stratum 
G Fannia sp. (juvenile) 


ILLINOIS BIOLOGICAL MONOGRAPHS 


BLAKE 


VOLUME X 


eet 


a ae 
DIY ee ee eS Bae 


Tee et Ell 


31 


PLATE XVI 


ip 


ILLINOIS BIOLOGICAL 
MONOGRAPHS 


Vol. X October, 1926 Mesva7) 40 4, 
S84; 
TAN 


A COMPARISON OF THE 
| ANIMAL COMMUNITIES OF CONIFEROUS 
: AND DECIDUOUS FORESTS 


WITH 16 PLATES AND 25 TABLES 


BY 
IRVING HILL BLAKE 


Price $1.50 


PUBLISHED BY THE UNIVERSITY OF ILLINOIS 
UNDER THE AUSPICES OF THE GRADUATE SCHOOL 
Urpana, ILLINoIs 


UNIVERSITY OF ILLINOIS STUDIES PUBLISHED 


ILLINOIS BIOLOGICAL MONOGRAPHS 


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No.1. The skull of Amiurus. With 8 plates. By J. E. Kindred. $1.25. 
No. 2. Contributions to the life histories of Gordius robustus Leidy and Paragordius varius 
(Leidy). With 21 plates. By H. G. May. $1.50. 
Nos. 3 and 4. Studies of Myxosporidia. A synopsis of genera and species of Myxosporidia, 
With 25 plates and 2 textfigures. By R. Kudo. $3.00. 
Vol. VI 
No. 1. The Nasal Organ in Amphibia. With 10 plates. By G. M. Higgins. $1.00. 
Nos. 2 and 3. Revision of the North American and West Indian species of Cuscuta. With 
13 plates. By T. G. Yuncker. $2.00. 
No. 4. The larvae of the Coccinellidae. With 6 plates. By J. H. Gage. 75 cents. 
Vol. VII 
No. 1. Studies on Gregarines, II. Synopsis of the polycystid Gregarines. With 4 plates. 
By Minnie Watson Kamm. $1.00. 
No. 2. The molluscan fauna of the Big Vermillion River, Illinois. With 15 plates. By F. C 
Baker. $1.25. 
No. 3. North American monostomes. By E. C. Harrah. $1.25. 
No. 4. A classification of the larvae of the Tenthredinoidea. With 14 plates. By H. Yuasa. 
$2.00. 
Vol. VIII 
No.1. The head-capsule of Coleoptera. With 26 plates. By F.S. Stickney. $2.00. 
No. 2. Comparative studies on certain features of Nematodes and their significance. With 
4 plates. By D. C. Hetherington. $1.00. 
(List continued on page 3 of cover.) 


Entered as second-class matter July 27, 1915, at the post-office at Urbana, Illinois, under the Act 
of August 24, 1912. Acceptance for mailing at the special rate of postage provided for 
in section 1102, Act of October 3, 1917, authorized July 31, 1918. 


ILLINOIS BIOLOGICAL MONOGRAPHS—Continued 


No. 3. Parasitic fungi from British Guiana and Trinidad. With 19 plates. By F. L. Stevens. 
$1.25. 
No, 4. The external Morphology and Postembryology of Noctuid Larvae. With 8 plates, 
By Lewis Bradford Ripley. $1.25. 
Vol. TIX 
No.1. The calciferous glands of Lumbricidae and Diplocardia. With 12 plates. By Frank 
Smith. $1.25. 
Nos. 2 and 3. A biologic and taxonomic study of the Microsporidia, With 27 plates and 9 text 
figures. By Roksabro Kudo. $3.00. 
No. 4. Animal ecology of an Illinois elm-maple forest. With 7 plates and 15 tables. By 
A. O. Weese. $1.25. 
Vol. X 
No. 1. Studies on the Avian species of the Cestode family Hymenolepididae. With 9 plates 
and 2 textfigures. By R. L. Mayhew. $1.50 
No, 2. Some North American Fish Trematodes. With 6 plates, 2 charts and 1 textfigure. 
By Harold Winfred Manter. $1.50 
No. 3. Comparative Studies on Furcocerous Cercariae. With 8 plates and 2 textfigures. By 
Harry Milton Miller, Jr. $1.25. 
No. 4. A Comparison of the Animal Communities of Coniferous and Deciduous Forests. 
With 16 plates and 25 tables. By Irving Hill Blake. $1.50. 


UNIVERSITY OF ILLINOIS STUDIES IN LANGUAGE AND LITERATURE 


The Studies in Language and Literature are designed to include monographs in gen- 
eral linguistics and comparative literature; the classical languages and Sanskrit; the Romance 
languages; and English, the Scandinavian, and other Germanic languages. The title of the 
series will be so construed as to admit the publication of such researches in the history of 
culture as may throw light on the processes of language and the interpretation of litera- 
ture. This series is published quarterly; the annual subscription price is three dollars. 


Vol. VI 
No. 1. La Coleccién Cervantina de la Sociedad Hisp4nica de América (The Hispanic Society 
of America): Ediciones de Don Quijote. By Homero Seris. $1.50. 
Nos.2and3. M. Tulli Ciceronis De Divinatione. Liber Primus. With commentary. By A. S. 
Pease. $3.00. 
No. 4. De Fragmenti suetoniani de grammaticis et rhetoribus; codicum nexu et fide. By 
R. P. Robinson. $2.00. 
Vol. VII 
No.1. Sir R. Howard’s comedy “The Committee.” With introduction and notes. By 
C. N. Thurber. $1.50. 
No. 2. The sepulchre of Christ in art and liturgy. By N.C. Brooks. With plates. $1.50. 
No. 3. The language of the Konungs Skuggsj4. By G. T. Flom. $1.50. 
No. 4. The significant name in Terence. By J. C. Austin. $2.00. 
Vol. VIII 
No. 1. Emerson’s theories of literary expression. By Emerson Grant Sutcliffe. $1.50. 
Nos. 2 and 3. M. Tulli Cicerone De Divinatione. Liber secundus. With commentary. By 
A. S. Pease. Parts I and II. $1.50. 
No. 4. The language of the Konungs Skuggsja. By G. T. Flom. Part II. $1.50. 


Vol. IX 
No.1. Studies in the narrative method of Defoe. By A. W. Secord. $1.50. 
No. 2. The manuscript-tradition of Plutarch’s Aetia Graeca and Aetia Romana. By J. B. 
Titchener. Price $1.00. 
No.3. Girolamo Fracastoro Naugerius, sive de poetica diologus. With translation by Ruth 
Kelso and introduction by Murry W. Bundy. $1.00. 
No. 4. The text-tradition of Pseudo-Plutarch’s Vitae Decem Oratorum. By Clarence George 
Lowe. $1.00. 
Vol. X 
No.1. Rhetorical Elements in the Tragedies of Seneca. By Howard Vernon Canter. $1.75. 
No. 2. Oriental affinities of Die Liigend von Sanct Johanne Chrysostomo. By Charles Allyn 
Williams. $1.00 
No. 3. The Vita Merlinit. By John Jay Parry. $1.50. 
N>4 The Bogarthing Law of the Codex Tunsbergensis. By G. T. Flom. $1.50 


UNIVERSITY OF ILLINOIS STUDIES IN THE SOCIAL SCIENCES _ 


The University of Illinois Studies in the Social Sciences are designed to afford a means 
of publishing monographs prepared by graduate students or members of the faculty in the 
departments of history, economics, political science, and sociology. Each volume will con- 
sist of about 600 printed pages annually. The subscription price is three dollars a year. 

Vol. V 
No. 2. The life of Jesse W. Fell. By Frances M. Morehouse. 60 cts. 
No. 4. Mine taxation in the United States. By L. E. Young. $1.50. 
Vol. VI 
Nos. i and 2. The veto power of the Governor of Illinois. By N. H. Debel. $1.00. 
No. 3. Wage bargaining on the vessels of the Great Lakes. By H. E. Hoagland. $1.50. 
No. 4.. The household of a Tudor nobleman. By P. V. B. Jones. $1.50. 
Vol. TX 
Nos. 1 and 2. War powers of the executive in the United States. By C. A. Berdahl. $2.25. 
No. 4. The economic policies of Richelieu. By F. C. Palm. $1.50. 
Vol. X 
No. 1. Monarchial tendencies in the United States, 1776-1801. By Louise B. Dunbar. 
; $2.25. - 
No. 2. Open Price Associations. By M. W. Nelson. $1.50. 
Nos. 3 and 4. Workmen’s representation in industrial government. By E. J. Miller. $2.00. 
Vol. XI 
Nos, 1 and 2, Economic aspects of southern sectionalism, 1840-1861. By R. R. Russel. 
$2.00. ; 
Nos. 2and 4. The Egyptian question in the relations of England, France, and Russia, 1832- 
1841. By F.S. Rodkey. $2.00. 
Vol. XII 
Nos. 1 and 2, Executive influence in determining Military Policy inthe U.S. By Howard 
White. $2.00. 
No. 3. Slave population at Athens during the V and IV Centuries B.C. By Rachel L. 
Sareent. $1.75. 
UNIVERSITY STUDIES 
GENERAL SEzIES, Vol. I, Il, If, and [V 
Partly out of print. A detailed list of numbers will be sent on request. 


PUBLICATIONS OF THE UNIVERSITY OF ILLINOIS 


Following is a partial list of the publications issued at the University: 

1. THe University oF Ittrois Srupres 1n LANGUAGE AND LITERATURE. Published 
quarterly. Three dollars a year. 

2. THE ILLINOIS BioLoGIcAL Monocrapss. Quarterly. Three dollars a year. 

3. TE University oF ILLINOIS STUDIES IN THE SOCIAL ScrencES. Monographs in his- 
tory, economics, political science, and sociology. Quarterly. Three dollars a year. 

4, Tur University Stupies. A series of monographs on miscellaneous subjects. 

5. THE JouURNAL oF ENGLISH AND GERMANIC PHItoLoGy. Quarterly. Three dollars 
a year. 

(For any of the above, address 161 Administration Building, Urbana, Illinois.) 

6. THE BULLETIN OF THE ENGINEERING EXPERIMENT STATION. Reports of the re- 
search work in the Engineering Experiment Station. Address Director of Engincering Experi- 
ment Station, University of Illinois. 

7. THE BULLETIN OF THE AGRICULTURAL EXPERIMENT STATION. Address Director of 
Agricultural Experiment Station, University of Ilinois. 

8. THE BULLETIN OF THE STATE NATURAL History Survey. Address Director of 
State Laboratory of Natural History, University of Illinois. 

9. THe BULLETIN oF THE STATE GEOLOGICAL SuRvEY. Address Director of State 
Geological Survey, University of Illinois. 

10. Tae BuLtetin oF THE STATE WATER SurvEY. Address Director of State Water 
Survey, University of Illinois. 

11. Tar BULLETIN oF THE ILLINOIS ASSOCIATION OF TEACHERS OF ENGLISH. Address 
301 University Hall, University of Linois. 

12. THe BULLETIN OF THE ScHOOL oF Epucation. Address 230 University Hall, 
University of Ilinois. 

13. The general series, containing the University catalog and circulars of special depart- 
ments, Address The Registrar, University of Illinois. 


